Resin useful for resist, resist composition and pattern forming process using the same

ABSTRACT

According to the present invention, a resist resin having in its structure a specific bridged-bond-containing aliphatic ring, and a resist composition comprising the same are provided. By using this resist composition, a resist pattern excellent in both transparency against short-wavelength light and dry-etching resistance can be formed by alkali development with high resolution.

FIELD OF THE INVENTION

[0001] The present invention relates to resins useful for resists, andto resist compositions comprising the same. The present invention alsorelates to a pattern forming process and a process for producingsemiconductors using the resist compositions.

BACKGROUND OF THE INVENTION

[0002] In manufacturing processes of electronic components such as LSIS,fine patterning techniques utilizing photolithography haveconventionally been adopted. Namely, a resist solution is firstly coatedonto the surface of a substrate or the like to form a resist film; andthe resist film is subjected to pattern-wise exposure to light, and thento treatments such as development by an alkaline developer to form aresist pattern. Subsequently, the bare surface of the substrate or thelike is dry-etched by utilizing this resist pattern as an anti-etchingmask to form minute lines and openings, and the remaining resist isfinally removed by means of ashing.

[0003] Therefore, the resist herein used is generally required to havehigh dry-etching resistance. From this point of view, resists containingaromatic compounds have widely been used. Specifically, there have beendeveloped a large number of resists containing, as base resins, novolakresins that are alkali-soluble.

[0004] On the other hand, in line with the trend toward high-density,high-integration LSIs and the like, the above-described fine patterningtechniques have been improved in recent years so that patterning can beattained at the level of sub-half micron order; and this tendency towardfine patterning is expected to be more remarkable. Indeed, thewavelengths of light sources for use in photolithography are being madeshorter; and it is now attempted to form fine resist patterns by usingArF excimer laser light (wavelength 193 nm), or a 5-fold higher harmonicwave of a YAG laser (wavelength 218 nm).

[0005] However, the resists containing, as base resins, resinscontaining aromatic compounds, which have commonly been used heretofore,have such a peculiarity that benzene nucleus contained in the compoundsshow high light absorption against the above-described short-wavelengthlight. Therefore, when it is tried to form a resist pattern, it isdifficult to allow light to fully reach the substrate side of a resistfilm when the film is exposed to light. It has thus been difficult toform, with high sensitivity and high accuracy, patterns excellent inshape.

[0006] Under such circumstances, there is a strong demand for thedevelopment of highly transparent resist resins suitable also forphotolithography which uses ArF excimer laser light, or a 5-fold higherharmonic wave of a YAG laser.

[0007] From this viewpoint, those resists containing alicyclic compoundsin place of aromatic compounds are now attracting attention. JapanesePatent Laid-Open Patent Publication No. 39665/1992, for instance,describes the following example: alkali-solubility is imparted to aresist which is excellent in both dry-etching resistance andtransparency against short-wavelength light and which comprises acompound containing adamantane that is a bridged-bond-containingalicyclic compound, by copolymerizing the resist and another acryliccompound; and a resist pattern is formed by alkali development, by theuse of this alkali-solubility-imparted resist.

[0008] As shown in Japanese Patent Laid-Open Publication No.199467/1995, there is known a resist material containing, astricyclodecanyl structure, an alicyclic compound having 5-memberedrings, which is one of bridged-bond-containing alicyclic compounds.

[0009] However, in the case where a resist pattern is formed by means ofalkali development by the use of a resist containing such an alicycliccompound, various problems will be brought about. This is because thealicyclic structure such as adamantane skeleton has extremely highhydrophobicity, so that the difference in alkali-solubility between thisalicyclic structure and a group which imparts alkali solubility to theresist is great.

[0010] For example, the predetermined area of the resist film cannot beuniformly dissolved and removed by development, so that the lowering ofresolution is brought about. Moreover, the lowering of resolution isalso caused due to the swelling of the resist pattern that occurs afterdevelopment, and the resist film is cracked or undergoes surfaceroughening because even the area of the resist film that is supposed toremain after development is partly dissolved. Further, the separation ofthe resist pattern is often caused due to the penetration of an alkalinesolution into the resist film-substrate interface. Furthermore, phaseseparation between the part having the alicyclic structure and the groupwhich imparts alkali solubility, such as carboxylic acid moiety, tendsto proceed in the polymer, so that it is difficult to obtain ahomogeneous resist solution. In addition, such a resist solution showspoor coating performance.

[0011] In order to reduce the hydrophobicity of these alicycliccompounds, the introduction of a polar group such as COOH or OH groupinto the alicyclic compounds has been proposed (Japanese PatentLaid-Open Publications No. 83076/1998, No. 252324/1995 and No.221519/1997). It has been confirmed that the solubility is considerablyimproved in all of these compounds.

[0012] However, the structure of these alicyclic compounds is such thatCOOH or OH group is combined with secondary or primary carbon atom ofthe aliphatic ring, so that this COOH or OH group tends to secondarilyreact with other substituents in the resists. Moreover, these compoundshave low glass transition temperatures, so that they tend to bring aboutthe lowering of resolution, and the swelling of the pattern afterdevelopment.

[0013] An object of the present invention is therefore to provide, byovercoming the aforementioned problems, a resist resin which can be acomponent of a resist composition having high transparency againstshort-wavelength light and high dry-etching resistance, capable offorming a resist pattern excellent in adhesion and resolution by meansof alkali development.

[0014] Another object of the present invention is to provide theabove-described resist composition.

[0015] A further object of the present invention is to provide a patternforming process using the resist composition.

SUMMARY OF THE TNVENTTON

[0016] Resist resin I according to the present invention is obtained byhomopolymerizing at least one monomer selected from monomers representedby the following general formulas (I-1) and (I-2):

[0017] wherein R is acryloyl or methacryloyl group, R₁₁ and R₁₂independently represent hydrogen atom or a monovalent alkyl group, andR₁₃ is OH group, ═O group, COOH group or COOR₁₄ group (R₁₄ is amonovalent organic group), or by copolymerizing the monomer(s) and anyother vinyl monomer.

[0018] Resist resin II according to the present invention comprises abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring.

[0019] Resist resin III according to the present invention comprises abridged-bond-containing aliphatic ring, at least one carbon constitutingthe bridged-bond-containing aliphatic ring being combined with oxygenthrough double bond.

[0020] A resist composition according to the present invention comprisesone of the above resist resins I, II and III, and a photo acidgenerator.

[0021] A pattern forming process according to the present inventioncomprises the steps of:

[0022] coating a resist composition comprising one of theabove-described resist resins onto a substrate, subjecting the resistcomposition coated onto the substrate to pattern-wise exposure, anddeveloping the resist composition exposed to light.

[0023] Further, a process for producing a semiconductor device accordingto the present invention comprises the steps of:

[0024] coating the above-described resist composition onto a substrate,

[0025] subjecting the resist composition coated onto the substrate topattern-wise exposure,

[0026] developing the resist composition exposed to light, therebyforming a patterned photomask, and

[0027] etching an etching film by dry etching, using the photomask as amask.

DESCRTPTION OF DRAWINGS

[0028] In the drawings,

[0029] FIGS. 1 to 3 are cross-sectional views showing processes forproducing semiconductor devices, using resist compositions of thepresent invention; and

[0030]FIGS. 4 and 5 are ¹H-NMR charts of Compounds (III-E) and (III-F),respectively, for use in the production of resist resins of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention relates to a resist resin obtainable byhomopolymerizing at least one monomer selected from monomers representedby the following general formulas (I-1) and (I-2):

[0032] or by copolymerizing the monomer(s) and any other vinyl monomer.

[0033] The present invention also relates to a resist resin having abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring.

[0034] Further, the present invention relates to a resist resincomprising a polymer or condensate of a monomer having abridged-bond-containing aliphatic ring composed of at least two ringsselected from the group consisting of 5-membered rings, 6-membered ringsand 7-membered rings, at least two oxygen-containing polar groups beingcombined with a tertiary carbon atom of the bridged-bond-containingaliphatic ring.

[0035] Furthermore, the present invention relates to a resistcomposition comprising the above-described resist resin, and a photoacid generator.

[0036] Furthermore, the present invention relates to a pattern formingprocess comprising the steps of coating the above-described resistcomposition onto a substrate, subjecting the resist composition coatedonto the substrate to pattern-wise exposure, and developing the resistcomposition exposed to light.

[0037] By the use of the resist resin, resist composition, and patternforming process according to the present invention, it is possible toform, by means of alkali development, a resist pattern excellent intransparency against short-wavelength light, dry-etching resistance, andresolution.

[0038] A resist composition according to the present invention comprisesas main components a resist resin and a photo acid generator. Thesecomponents will be explained in detail hereinafter.

[0039] <Resist Resins>

[0040] Resist resins according to the present invention will bedescribed hereinafter.

[0041] [Resist Resin I]

[0042] In one aspect of the present invention, resist resin I isobtained by homopolymerizing at least one monomer selected from monomersrepresented by the following general formulas (I-1) and (I-2):

[0043] wherein R is acryloyl or methacryloyl group, R₁₁ and R₁₂independently represent hydrogen atom or amonovalent alkyl group, andR₁₃ is OH group, ═O group, COOH group or COOR₁₄ group (R₁₄ is amonovalent organic group), or by copolymerizing the monomer(s) and anyother vinyl monomer.

[0044] In the monomers represented by the general formulas (I-1) and(I-2), R₁₁ and R₁₂ are hydrogen atom or a monovalent alkyl group. Sincethese groups are released and decomposed more sensitively in thepresence of an acid, the resist resin becomes alkali-soluble. It ispreferable that R₁₁ and R₁₂ be not hydrogen atom at the same time, butmethyl, ethyl, propyl or isopropyl group because the latter groups arereleased and decomposed more sensitively than hydrogen atom.

[0045] R₁₃ is OH group, ═O group, COOH group, or COOR₁₄ group (R₁₄ is amonovalent organic group). Since the resist resin contains R₁₃, it showsreduced hydrophobicity. By introducing this group, it has becomepossible to improve the adhesion between a photosensitive resistcomposition and a substrate, and the alkali-solubility of a polymer. Inorder to enhance this function, a plurality of R₁₃s may be introduced.In particular, ═O group is preferred because it hardly causesundesirable reaction with other groups introduced as side chains. It ispreferable that OH group, COOH group or COOR₁₄ group (R₁₄ is amonovalent organic group) introduced as R₁₃ is combined with a tertiarycarbon atom as will be described in [Resist Resin II]. Further, althoughR is acryloyl or methacryloyl group, acryloyl or methacryloyl groupsubstituted with cyano group or halogen atom is also included in thescope of the present invention.

[0046] In the case where a copolymer of a monomer represented by thegeneral formula (I-1) or (I-2) and another vinyl monomer is used, thecontent of the monomer represented by the general formula (I-1) or (I-2)is preferably from 10 to 90 mol %, more preferably from 30 to 70 mol %of the copolymer. When this monomer content is less than 10 mol %, theremay not fully be obtained such a function that the unexposed area of theresist resin remains closely adhered to a substrate and keepsdry-etching resistance high, while the exposed area of the resist resinreleases the alicyclic structure to increase the alkali-solubility ofthe polymer. In contrast, when the monomer content exceeds 90 mol %, itbecomes difficult to control the alkali-solubility of the polymer, sothat the production cost tends to increase.

[0047] The vinyl monomer that is copolymerized with a monomerrepresented by the general formula (I-1) or (I-2) is preferably at leastone monomer selected from monomers represented by the following generalformulas (I-3), (I-4), (I-5), (I-6) and (I-7):

[0048] wherein R₃₁ represents hydrogen atom, or at least one groupselected from the group consisting of OH group, OR₁₄ group (R₁₄ is amonovalent organic group) and ═O group, R₃₂ represents hydrogen atom ora monovalent organic group, and R₄₁ represents vinyl, acryloyl ormethacryloyl group.

[0049] When any of these monomers is copolymerized with a monomerrepresented by the general formula (I-1), a copolymer having improvedalkali-solubility and dry-etching resistance can be obtained. Such acopolymer can therefore impart further improved functions to a resistcomposition. In particular, when a monomer represented by the generalformula (I-7) is used, the resulting copolymer shows improveddry-etching resistance, so that the use of this monomer is morepreferred. Further, a monomer represented by the formula (I-2) is morepreferable than a monomer represented by the formula (I-1); a monomerrepresented by the formula (I-4) is more preferable than a monomerrepresented by the formula (I-3); and a monomer represented by theformula (I-6) is more preferable than a monomer represented by theformula (I-5). This is because monomers represented by the formulas(I-2), (I-4) and (I-6) have higher carbon contents than thoserepresented by the formulas (I-1), (I-3) and (I-5), respectively, sothat the former monomers are more excellent than the latter monomers inresistance to ordinary energy gases such as CF₄.

[0050] Further, vinyl monomers other than monomers represented by theabove general formulas (I-3), (I-4), (I-5), (I-6) and (I-7) may also beused. In this case, it is desirable that the vinyl monomers havebridged-bond-containing alicyclic structure. The bridged-bond-containingalicyclic structure includes cyclic cyclo or bicyclo compoundsrepresented by the general formula C_(n) H_(2n) (n is an integer of 3 ormore), and condensed rings thereof. Specific examples of this structureinclude cyclobutane ring, cyclopentane ring, cyclohexane ring,cycloheptane ring, cross-linked-hydrocarbon-introduced cyclobutane,cyclopentane, cyclohexane and cyclopentane rings, spiro rings such asspiroheptane and spirooctane, terpene rings such as norbonyl ring,adamantyl ring, bornene ring, menthyl ring and menthane ring, steroidalskeletons such as thujane, sabinene, thujone, carane, carene, pinane,norpinane, bornane, fenchane, tricyclene and cholesteric rings, bileacid, digitaloides, camphor ring, isocamphor ring, sesquiterpene ring,santone ring, diterpene ring, triterpene ring, and steroid saponins.

[0051] Further, it has been known that, since the wavelengths ofabsorption bands are shifted not only by alicyclic structure but alsocondensed polycyclic structure, the transparency at 193 nm can beensured even by condensed polycyclic structure (T. Ushirogouchi et al.,Proc. SPIE, Vol. 2195 (1994), page 205, etc.). Therefore, the object ofthe present invention can be attained even by vinyl monomers havingcondensed polycyclic structure.

[0052] Examples of vinyl monomers having condensed polycyclic structureare as follows: indene, indane, benzofulvene, 1-indanone, 2-indanone,1,3-indandione, ninhydrin, naphthalene, methylnaphthalene,ethylnaphthalene, dimethylnaphthalene, cadalene, vinylnaphthalene,1,2-dihydronaphthalene, 1,4-dihydronaphthalene,1,2,3,4-tetrahydronaphthalene tetralene,1,2,3,4,5,6,7,8-octahydronaphthalene, cis-decalene, trans-decalene,fluoronaphthalene, chloronaphthalene, bromonaphthalene, iodonaphthalene,dichloronaphthalene, (chloromethyl)naphthalene, 1-naphthol, 2-naphthol,naphthalene diol, 1,2,3,4-tetrahydro-1-naphthol,1,2,3,4-tetrahydro-2-naphthol, 5,6,7,8-tetrahydro-1-naphthol,5,6,7,8-tetrahydro-2-naphthol, decahydro-1-naphthol,decahydro-2-naphthol, chloronaphthol, nitronaphthol, aminonaphthol,methoxynaphthalene, ethoxynaphthalene, naphthyl ether, naphthyl acetate,naphthoaldehyde, naphthalene dicarbaldehyde, hydroxynaphthoaldehyde,dinaphthyl ketone, 1(2H)-nephthalene, alpha-tetralone, beta-tetralone,alpha-decalone, beta-decalone, 1,2-naphthoquinone, 1,4-naphthoquinone,2,6-naphthoquinone, 2-methyl-1,4-naphthoquinone,5-hydroxy-1,4-naphthoquinone, isonaphthazaline, naphthoeic acid,1-naphthol-4-carboxylic acid, naphthalic acid, naphthalic anhydride,1-naphthylacetic acid, thionaphthol, N,N-dimethylnaphthylamine,naphthonitrile, nitronaphthalene, pentalene, azulene, heptalene,fluorene, 9-phenylfluorene, nitrofluorene, 9-fluorenol, fluorenone,anthracene, methylanthracene, dimethylanthracene,9,10-dihydroanthracene, anthrol, anthranol, hydroanthranol,dihyroxyanthracene, anthragallol, 1(4H)-anthracenone, anthrone,anthrarobin, chrysarobin, oxanthrone, anthracenecarboxylic acid,anthramine, nitroanthracene, anthracenequinone, anthraquinone,methylanthraquinone, hydroxyanthraquinone, phenanthrene, phenanthrol,phenanthrenehydroquinone, phenanthraquinone, biphenylene, s-indacene,as-indacene, phenarene, teracene, chrysene, 5,6-chrysoquinone, pyrene,1,6-pyrenequinone, triphenylene, benzo[alpha]anthracene,benzo[alpha]anthracene-7,12-quinone, benzanthrone, aceanthrene,acephenanthrylene, acephenanthrene, 17Hcyclopeneta[alpha]-phenanthrene,fluoranthene, pleiadene, pentacene, pentaphen, picene, pirylene,dibenzo[a,j]anthracene, benzo[alpha]pyrene, coronene, pyranthrene, andpyranthrone.

[0053] The resist resin according to the present invention can beobtained by polymerizing, by means of radical, cationic or anionicpolymerization, a polymerizable compound having, in its molecule,alicyclic structure into which an acidic substituent has beenintroduced, and polymerizable double bond. In general, a monomer havingpolymerizable double bond like one in an alicylic group contained inpolymer backbone can produce a high-molecular-weight polymer when it issubjected to cationic or anionic polymerization. However, in the presentinvention, even if the molecular weight of the resist resin is low,there is no problem as long as a film can be formed by the use of theresin. Therefore, the polymerization may be conducted by a simpletechnique such as radical polymerization, and the resulting polymer thatis a mixture of low-molecular-weight compounds and high-molecular-weightcompounds may also be used as the resist resin.

[0054] At this time, the polymerizable compound may also becopolymerized with acrylic acid, maleic anhydride, an ester substitutionproduct of acrylic acid or maleic anhydride, vinyl phenol, vinylnaphthol, hydroxyethyl methacrylate, SO₂, or the like.

[0055] Further, it is also possible to control the alkali-solubility ofthe polymer, and to improve the adhesion between the resist and asubstrate by copolymerizing the polymerizable compound and analkali-soluble compound whose alkali-soluble group has been protected bya group decomposable by an acid, having dissolution-preventing ability.However, when the transparency of the resist against short-wavelengthlight is taken into consideration, it is preferable to copolymerize thepolymerizable compound and a compound having no molecular skeleton whoselight absorption in short-wavelength ranges is great, such as benzenenucleus. Specifically, it is desirable that the absorbance of thepolymer against light having a wavelength of 193 nm be 4 or less,preferably 2 or less per 1 micrometer. In the case where the resistcomposition of the present invention is used as an upper resist to becoated onto a substrate having an intermediate layer, the aboveabsorbance may be made as high as approximately 8 per 1 micrometer.

[0056] It is preferable to make the average molecular weight of theresist resin according to the present invention in the range of 1,000 to500,000, more preferably in the range of 3,000 to 50,000. A resist resinhaving an average molecular weight of less than 1,000 is unfavorable forforming a resist film having sufficiently high mechanical strength. Onthe contrary, when the average molecular weight of the resist resin ismade higher than 500,000, it becomes difficult to form a resist patternexcellent in resolution. These compounds are, in general, mixtures ofthe compound of the present invention and other copolymers havingvarious molecular weights.

[0057] The resist resin according to the present invention shows itseffects even when it has a relatively low molecular weight; and even ifthe average molecular weights of the components of the resin arelocalized in the range of, for example, 500 to 1,000, the resist resinis prevented from being dissolved unevenly. Therefore, such a resin isalso desirable one. Moreover, in this case, even if the monomers areremaining in the resin in a large amount, the dissolution properties anddry-etching resistance of the resin are hardly marred.

[0058] [Resist Resin II]

[0059] Resist resin II according to the present invention comprises, inits main or side chain, a bridged-bond-containing aliphatic ring, atleast two oxygen-containing polar groups being combined with a tertiarycarbon atom of the bridged-bond-containing aliphatic ring.

[0060] In the resist resin II according to the present invention, atleast two oxygen-containing polar groups are combined with a tertiarycarbon atom of the above-described bridged-bond-containing aliphaticring. When three or more oxygen-containing polar groups are combinedwith a tertiary carbon atom of the above-describedbridged-bond-containing aliphatic ring, these groups can highlycontribute to the improvement in adhesion between the resin and asubstrate, and in the alkali-solubility of the resin. Therefore, such aresin is more preferred.

[0061] The oxygen-containing polar groups combined with onebridged-bond-containing aliphatic ring may be the same or different.

[0062] In the present invention, the oxygen-containing polar group is asubstituent having carbon-oxygen bond, a difference in electronegativitybetween carbon and oxygen being great. Examples of such a group includesubstituted or unsubstituted carboxyl groups, substituted orunsubstituted cyclic lactone groups, substituted or unsubstitutedhydroxyl groups, aldehyde group, groups containing peroxides,substituted or unsubstituted urethane groups, acyl groups, and carbonategroups.

[0063] When the oxygen-containing polar groups are combined with atertiary carbon atom of the bridged-bond-containing aliphatic ringthrough —(CH₂)_(n)— (n is a natural number), these polar groups havehigh degree of freedom of movement. Therefore, there cannot be obtainedthe effects equal to those obtainable when the oxygen-containing polargroups are combined directly with a tertiary carbon atom of thebridged-bond-containing aliphatic ring. For this reason, such a case isexcluded from the state of “oxygen-containing polar groups combined witha tertiary carbon atom”.

[0064] In view of the properties of the resist composition, it isparticularly desirable when polarity is taken into consideration thatthe oxygen-containing polar group be at least one organic group selectedfrom substituted or unsubstituted carboxyl groups, substituted orunsubstituted hydroxyl groups, and substituents containing cycliclactones. By the use of these groups, the effects of improving adhesionand solubility can be obtained.

[0065] Further, such an oxygen-containing polar group is preferred thatthe substituent introduced to the carboxyl group be a cyclic lactone. Itis also preferable that the carboxyl group form an acid anhydridetogether with another bridged-bond-containing alicyclic compound havinga carboxylic acid. This is because a compound having such anoxygen-containing polar group shows particularly increased solubility.

[0066] Furthermore, the bridged-bond-containing aliphatic ring maycontain not only two or more oxygen-containing polar groups at atertiary carbon atom of the ring, but also a non-reactive polar groupsuch as ketone or lactone introduced to the secondary or primary carbonatom of the ring.

[0067] The resist resin II reveals its effects through the followingaction.

[0068] The above-described oxygen-containing polar group is restrictedin its movement around carbon as compared with the conventional casewhere the polar group is combined with carbon at the secondary or primaycarbon atom. For instance, in the case of a resin having abridged-bond-containing aliphatic ring in which hydroxyl group isintroduced to the carbon atom, the hydroxyl group has freedom ofmovement only in the direction around the carbon, and the molecularmotion of the hydroxyl group is thus small. In contrast, when hydroxylgroup is introduced to carbon at the secondary or primary carbon atom ofthe ring, it has freedom of movement not only in the direction aroundthe carbon but also in the direction parallel to the carbon. Themolecular motion of such hydroxyl group is thus great.

[0069] For this reason, when a resin having a bridged-bond-containingaliphatic ring, oxygen-containing polar groups being introduced totertiary carbon atom of the bridged-bond-containing aliphatic ring isused as the base resin of a resist composition, the free volume isdecreased, so that the resist composition has a high glass transitiontemperature (Tg). As a result, high resolution can be obtained.

[0070] In fact, when a resin having such a structure that OH group hasbeen introduced to carbon at the 2-position of a bridged-bond-containingaliphatic ring is compared with a resin having such a structure that OHgroup has been introduced to tertiary carbon atom of abridged-bond-containing aliphatic ring, the latter is found to have a Tgabout 10 to 20° C. higher than that of the former. Moreover, a resin inwhich OH group has been introduced to an alicyclic skeleton throughmethylene, like conventionally known hydroxymethyltricyclodecanylacrylate compounds, has a Tg 10 to 20° C. lower than the above-describedresin having OH group at the secondary carbon atom of thebridged-bond-containing aliphatic ring. Therefore, the differencebetween this resin and the resin having OH group at the 3-position ofthe bridged-bond-containing aliphatic ring becomes more evident.

[0071] In addition, since the molecular motion of OH group introduced totertiary carbon atom of the ring is small as mentioned previously, adeveloper hardly penetrates the unexposed area. Therefore, the patternscarcely swells.

[0072] Moreover, the resin according to the present invention shouldhave two or more oxygen-containing polar groups introduced to tertiarycarbon atom of a bridged-bond-containing aliphatic ring. These groupsplay an important role in improvement in adhesion to a substrate andalkali-solubility which are the essential properties of resists. Sincethese groups are combined with tertiary carbon atom, they have freedomof movement only in the direction around the carbon, and cannot turnlaterally. It is therefore highly probable that these groups turn tooutside in terms of the backbone. For this reason, the resin has highercompatibility with an alkaline solvent that is brought into contact withthe resin, and higher adhesion to a substrate.

[0073] Oxygen-containing polar groups, especially OH group and COOHgroup, combined with carbon at the secondary or primary carbon atom showhigh reactivity, so that they tend to cause secondary cross-linkingreaction by heating. In particular, chemically amplified positiveresists have such a crucial problem that pattern formation cannot beattained while they are processed by heating. This tendency can be moreremarkable when the resin has acid anhydride structure.

[0074] However, oxygen-containing polar groups combined with tertiarycarbon atom as in the present invention show low reactivity, and hardlycause secondary cross-linking reaction when heated. Therefore, theaforementioned problem is not brought about in this case.

[0075] Thus, according to the present invention, it is possible to form,by alkali development, a resist pattern excellent in transparencyagainst short-wavelength light, dry-etching resistance, adhesion andresolution.

[0076] In the resist resin II according to the present invention, thepercentage of the bridged-bond-containing alicyclic ring is desirablyfrom 20 to 90% by weight of the resin. When this percentage is notwithin this range, the resist resin has reduced dry-etching resistanceor alkali-solubility.

[0077] In the resin according to the present invention, it is desirablethat at least one of the above-described oxygen-containing polar groupsbe COOH group protected by a dissolution-preventive group (a solublegroup which can be decomposed by an acid). If the resin has such agroup, the resist layer shows alkali-solubility after it has causeddeprotection reaction by an acid. Further, the rate of dissolution ofthe unexposed area is reduced due to the existence of the protectivegroup, so that high dissolution contrast can be attained. In addition,since the resin has hydrophilicity, the alkali-solubility of the resinis also maintained properly.

[0078] In particular, a resin obtained by copolymerizinghydroxyadamantyl acrylate having hydroxyl group combined with tertiarycarbon atom and tetrahydropyranyl acrylate can be mentioned as anexample of the resin having the above-described protective group. Thisresin has, in its unexposed area, no alkali-soluble group but hashydroxyl group protruding from its polymer chain; the resin thus showsincreased hydrophilicity. Therefore, the unexposed area of the resistfilm will never be unevenly dissolved. In addition, the resist filmshows increased adhesion to a substrate.

[0079] Furthermore, it is desirable that the resin in the presentinvention contains acid anhydride structure in its structure, that is,in its main or side chain, and that at least one of the above-describedoxygen-containing polar groups is hydroxyl group. Namely, in the casewhere the resin contains, in its structure, both OH group that is notinvolved in linkage, and acid anhydride structure, a secondaryself-crosslinking reaction is suppressed. Therefore, the effects of thepolar groups combined with tertiary carbon atom become remarkable, andthe resin shows high contrast. Such a resin is thus desirable as apositive resist.

[0080] The resin according to the present invention can be obtained bypolymerizing or condensing starting monomers in one of the followingcombinations i) to iv), by any of various means such as radicalpolymerization or living polymerization:

[0081] i) a combination of one or more monomers comprising abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with tertiary carbon atom of thebridged-bond-containing aliphatic ring (structure A);

[0082] ii) a combination of one or more monomers having the structure A,and one or more monomers comprising a bridged-bond-containing aliphaticring, least two oxygen-containing polar groups being combined withsecondary or primay carbon atom of the bridged-bond-containing aliphaticring (structure B);

[0083] iii) a combination of one or more monomers having the structureA, and one or more monomers having structure (structure C) that isneither the structure A nor the structure B; and

[0084] iv) a combination of one or more monomers having the structure A,one or more monomers having the structure B, and one or more monomershaving the structure C.

[0085] The bridged-bond-containing aliphatic ring and oxygen-containingpolar groups contained in the structure A or B can include thepreviously-mentioned bridged-bond-containing aliphatic rings andoxygen-containing polar groups, respectively.

[0086] In the case where the resin according to the present invention isobtained by using monomers in the above combination (i) or (ii), it isdesirable that the oxygen-containing polar groups combined with thebridged-bond-containing aliphatic ring contained in the resin becombined with tertiary carbon atom as many as possible. It is sufficientthat at least 70%, more preferably 90% or more of the oxygen-containingpolar groups combined with the bridged-bond-containing aliphatic ringare combined with tertiary carbon atom of the ring. There may be such acase that a monomer having the structure A is to contain a monomerhaving oxygen-containing polar groups combined with carbon at the2-position due to the side reaction caused when the former monomer issynthesized, inevitably becoming equal to the above combination (ii).Such a case is also permissible.

[0087] When the resin according to the present invention is obtained byusing monomers in the combination of (iii) or (iv), the effects of themonomer in which oxygen-containing polar groups are introduced totertiary carbon atom can be observed when the monomer having thestructure A exceeds at least 15%, more preferably 20% or more of thetotal molar amount of the monomers constituting the resin, although thispercentage may vary depending upon the copolymerization ratio of themonomer having the structure A to the other monomers.

[0088] A monomer useful as the starting monomer in the presentinvention, having a bridged-bond-containing aliphatic ring, at least twooxygen-containing polar groups being combined with tertiary carbon atomof the bridged-bond-containing aliphatic ring (structure A) can beobtained by oxidizing an alicyclic compound, and extracting the desiredcomponent. Alternatively, the above monomer can conveniently be obtainedby partly hydrolyzing an alicyclic compound by bromination, or by meansof air oxidation using a catalyst (Japanese Patent Laid-Open PublicationNo. 35522/1999). Further, it is also possible to use acrylated ormethacrylated compounds obtained by further subjecting theabove-obtained compounds to addition reaction using a catalyst, or toesterification to be carried out by an acid chloride process.

[0089] In the case where the resin of the present invention is obtainedby polymerization, it is desirable to use a monomer having the structureA, and, as a monomer having another structure, an acrylic or vinylcompound. It is particularly preferable to use, as the monomer, anacrylic compound to obtain an acrylic or methacrylic resin because it isreadily polymerizable. An acrylic or methacrylic resin can be obtainedby polymerizing, as the monomer having the structure A, a monomer whosebridged-bond-containing aliphatic ring contains, as theoxygen-containing polar groups, at least one acryloyloxy ormethacryloyloxy group. The acryloyloxy or methacryloyloxy group may besubstituted with cyano group or halogen atom.

[0090] In particular, when the resin of the present invention isobtained by polymerizing, as the monomer having the structure A, acompound represented by the following general formula (II-1) or (II-2),it shows excellent dry-etching resistance, solubility and adhesion, andhas a high glass transition temperature; such a resin is thus desirable.

[0091] wherein R₁ represents acryloyl or methacryloyl group, R₂represents hydrogen atom or an oxygen-containing polar group, and R₃represents hydrogen atom, a group decomposable by an acid, a cyclicsubstituent having a lactone, or a substituent having acid anhydridestructure formed with a bridged-bond-containing alicyclic compoundcontaining a carboxylic acid.

[0092] Examples of the group for R₃, decomposable by an acid includetert-butyl group, tetrahydropyranyl group and acetal group. Further, inorder to obtain high contrast between exposed and unexposed areas, it isdesirable that R₃ can also act as a dissolution-preventive group.

[0093] wherein R₁ represents acryloyl or methacryloyl group, R₂represents hydrogen atom or an oxygen-containing polar group, and R₄represents hydroxyl group, a cyclic substituent having a lactone, or asubstituent having acid anhydride structure formed with abridged-bond-containing alicyclic compound containing a carboxylic acid.

[0094] In the case where the resin of the present invention is obtainedby condensation, the resin is desirably an alicyclic-backbone-typepolymer or oligomer obtainable by dehydration condensation, using, asthe monomer having the structure A, a monomer having abridged-bond-containing aliphatic ring in which two or more organicgroups of at least one of carboxyl group and hydroxyl group are combinedwith tertiary carbon atom, or a monomer further having lactone structureat tertiary carbon atom.

[0095] In the above-described polymer or oligomer, the monomer iscombined with the backbone of the polymer through linkage decomposableby an acid. Examples of this linkage include ester linkage and acidanhydride linkage. In this case, the resin is of alicyclic backbonetype, and has polyester or polyacid anhydride structure.

[0096] When the resin has the polyester or polyacid anhydride structureof alicyclic backbone type, the resist composition undergoes, before andafter exposure, drastic decomposition of the molecular skeletonincluding the backbone of the resin, and high resolution can thus beobtained. Moreover, the number of free secondary oxygen-containing polargroups is small in this resin, so that dehydration condensation sidereaction is scarcely caused and that the resin has a high Tg. Such aresin is therefore desirable. Further, since the resin hasbridged-bond-containing alicyclic structure, the solubility of theexposed area of the resist is remarkably improved with the coatingperformance and adhesion of the resist maintained high. Moreover, thedissolution contrast between exposed area and unexposed area can beimproved. In addition, since the resist has bridged-bond-containingalicyclic structure in its backbone, it can also show sufficiently highdry-etching resistance.

[0097] In particular, when the resin according to the present inventionhas a polyester or polyacid anhydride linkage that is formed bydehydration condensation between carboxyl group and hydroxyl group,and/or between carboxyl groups, the resin is excellent in the propertyof being decomposed by an acid, has high stability and hightransparency, and can readily be synthesized. This resin is thusdesirable.

[0098] The above-described ester linkage is obtained by the dehydrationcondensation of a polyvalent carboxylic acid with an alicyclicpolyvalent alcoholic compound, using a catalyst; or by the desalting ofa polyvalent carboxylic acid chloride with a polyvalent alcoholiccompound. Alternatively, the ester linkage may be obtained by thedehydration condensation of one or more compounds containing a pluralityof carboxyl groups and alcohol groups.

[0099] The above-described acid anhydride linkage is obtained by thedehydration condensation of one or more polyvalent carboxylic acidcompounds.

[0100] The resin may contain several types of linkage (e.g., esterlinkage and acid anhydride linkage) at the same time when the linkage ofdifferent types is formed by the same type of reaction, especially bydehydration condensation reaction.

[0101] In general, polymers or oligomers containing acid anhydridelinkage have such an advantage that they are excellent inalkali-solubility. It is generally considered that these acid anhydridecompounds are readily hydrolizable and unstable. However, acid anhydridelinkage that is interposed between bulky alicyclic compounds as in thepresent invention is extremely stable, and imparts alkali-solubilitysuitable for pattern formation. On the other hand, polymers or oligomershaving ester linkage are stable in any solvent, and show a great changein dissolution rate as the decomposition of an acid catalyst proceeds,so that they have the advantage of improving the resolution. By usingthese different types of linkage in combination, the solubility andresolution that are more preferable for resists can be obtained at thesame time. In this case, it is sufficient that the ratio of acidanhydride linkage to ester linkage is from 1:20 to 5:1; and, morepreferably, the acid anhydride linkage content is 10% or more and lessthan 50%.

[0102] Further, a resin containing acid anhydride structure in itsstructure, that is, in the main or side chain, wherein at least one ofthe above-described oxygen-containing polar groups is hydroxyl group isdesirable as the resin of the present invention as mentioned previously.

[0103] Such a resin may be obtained by polymerizing or condensing, inthe previously mentioned manner, a monomer having the structure A inwhich at least one of the oxygen-containing polar groups is hydroxylgroup. For instance, not only poly(ester-acid anhydride) compounds butalso copolymers comprising alicyclic structure having OH group at its3-position, and maleic anhydride can be mentioned.

[0104] On the other hand, examples of compounds having the structure Cinclude the following: tert-butyl acrylate, tert-butyl methacrylate,methacrylic acid, acrylic acid, alpha-chloroacrylic acid and estersthereof, trifluoromethyl acrylate, alpha-methylstyrene, trimethylsilylmethacrylate, trimethylsilyl alpha-chloroacrylate, trimethylsilylmethylalpha-chloroacrylate, maleic anhydride, tetrahydropyranyl methacrylate,tetrahydropyranyl alpha-chloroacrylate, methyl methacrylate,t-butylalpha-chloroacrylate, butadiene, glycidyl methacrylate, isobornylmethacrylate, menthyl methacrylate, norbornyl methacrylate, adamantylmethacrylate, cycloolefin compounds, acrylates having lactone skeletonin acrylic side chains, and acrylates having epoxy skeleton. Of these,tetrahydropyranyl methacrylate and maleic anhydride are particularlypreferable for improving the resolution because they do not causesecondary reaction that is commonly caused. Further, in order to improvethe dry-etching resistance of a resin, cycloolefin compounds areconveniently used as comonomers; and in order to improve thedevelopability, acrylic compounds having lactone skeleton in the sidechains thereof are conveniently used as comonomers.

[0105] In the case where the resin according to the present invention isan arylic or methacrylic resin, the weight-average molecular weight (Mw)of the resin, calculated in terms of polystyrene, is preferably from2,000 to 100,000, more preferably from 5,000 to 60,000 although it mayvary depending upon the desired properties of the resist composition.When the Mw is less than 2,000, the resin tends to have poorfilm-forming properties. On the other hand, when the Mw is in excess of100,000, the resin tends to have decreased developability andresolution. Further, the molecular-weight distribution Mw/Mn ispreferably from 1 to 5, more preferably from 1 to 2.

[0106] Further, in the case where the resin according to the presentinvention is a polyester or polyacid anhydride condensate of alicyclicbackbone type, it is preferable to adjust the average molecular weightof the resin, calculated in terms of polystyrene to 100-30,000. A resinhaving an average molecular weight of less than 100 is unfavorable forforming a resist film excellent in mechanical strength, heat resistance,and coating performance. On the other hand, when the average molecularweight of the polymer compound is in excess of 30,000, the compound hasimpaired alkali-solubility, so that it becomes difficult to form aresist pattern with high resolution. These compounds are generallymixtures of components having various molecular weights.

[0107] The resin of the present invention reveals its effects even whenit has relatively low molecular weight like a dimer; and, even such aresin that the average molecular weights of its components arelocalized, for example, to the range of 100 to 1,000 is also effective.Further, in this case, even if less than 10% of the monomers isremaining in the copolymer, the copolymer scarcely undergoesdeterioration of dissolution properties or dry-etching resistance.

[0108] [Resist Resin III]

[0109] Resist resin III that is the base of a resist composition of thepresent invention comprises a bridged-bond-containing aliphatic ring inits structure.

[0110] The bridged-bond-containing aliphatic ring is a combination of atleast two aliphatic rings selected from 5-membered rings, 6-memberedrings and 7-membered rings. The aliphatic rings may be either the sameor different in terms of the number of members constituting one ring. Inaddition, the bridged-bond-containing alicyclic skeleton may contain, inaddition to carbon, such elements as oxygen, sulfur and nitrogen.

[0111] The above bridged-bond-containing aliphatic ring can includethose aliphatic rings enumerated in the item of [Resist Resin I].

[0112] The resist resin III according to the present invention containsthe above-described bridged-bond-containing aliphatic ring in itsstructure, at least one of the carbons constituting thebridged-bond-containing aliphatic ring being combined with oxygenthrough double bond to form >C═O.

[0113] It is desirable that the resin according to the present inventionbe incorporated into a resist composition so that the amount of >C═Owill be 40% by weight or more of the solid matter of the resistcomposition. When this amount is less than 40% by weight, it isdifficult to obtain, by alkali development, a resist pattern excellentin both resolution and adhesion. Moreover, the resulting resist patternmay have impaired dry-etching resistance.

[0114] Further, the resin according to the present invention may be aresin having the above-described bridged-bond-containing alicyclicskeleton in its structure, at least one of the rings constituting thebridged-bond-containing alicylic skeleton being a lactone ring; that is,a resin containing —C(═O)—O— in one ring.

[0115] A resin having such bridged-bond-containing alicyclic skeletoncontaining a lactone ring is to have further improved alkali-solubility,dry-etching resistance and adhesion.

[0116] When the bridged-bond-containing alicyclic skeleton in the resinis a lactone ring, the resin can show hydrophilicity higher than that ofa resin to which a substituent containing OH, sulfonyl or nitro grouphas been introduced as mentioned in PRIOR ART. Moreover, since such aresin is not so reactive as a resin having a substituent containing OHgroup, side reaction by which a resist is made negative hardly occurs.

[0117] In this case, it is preferable that the components are soincorporated that the amount of lactonyl group will be 30 mol % or moreof the resin. When this amount is less than 30 mol %, it is difficult toform, by alkali development, a resist pattern excellent in bothresolution and adhesion. Moreover, the resulting resist pattern tends tohave decreased adhesion.

[0118] The resin of the present invention can be made in the followingmanner (a) or (b). (a) Some of the carbons contained in an alicycliccompound having the above-described bridged-bond-containing aliphaticring are oxidized by the use of a strong oxidizing agent. By this,methylene carbon contained in the bridged-bond-containing aliphatic ringis oxidized, and an alicyclic compound (alicyclic compound (A)) havingthe bridged-bond-containing aliphatic ring into which >O═O has beenintroduced can be obtained.

[0119] By further allowing the oxidizing agent to act on this compoundto cause oxidation, —O— is introduced into the ring. Thus, there can beobtained an alicyclic compound (alicyclic compound (B)) having thebridged-bond-containing aliphatic ring whose bridged-bond-containingalicyclic structure has been made into a lactone ring.

[0120] A resin according to the present invention can then be obtainedby homopolymerizing, as a monomer, the above alicylcic compound (A) or(B), or a derivative thereof obtained by introducing, into the alicycliccompound (A) or (B), a group that can act as a binding member during thepolymerization step to be conducted later, or by copolymerizing such amonomer and any other monomer.

[0121] (b) A resin according to the present invention can be obtained byallowing a strong oxidizing agent to react with some of the carbonsconstituting a resin having the above-described bridged-bond-containingalicyclic skeleton to oxidize the carbons.

[0122] Specifically, the following [1] or [2] can be mentioned as thepolymerization method described in the above (a).

[0123] [1] The alicyclic compound (A) or (B) which is a monomer usefulfor synthesizing a resin according to the present invention, or, as itsderivative, a compound having polymerizable double bond is polymerizedby means of radical, anionic, or cationic polymerization, orpolymerization using a Ziegler-Natta catalyst. In general, a monomerhaving polymerizable double bond, such as one having alicyclic moiety inits main chain, can yield a polymer having a higher molecular weightwhen it is polymerized by the use of a Ziegler-Natta catalyst. However,the resin according to the present invention brings about no problem aslong as it can form a film even if the molecular weight of the resin islow. Therefore, the monomer may be polymerized by a simple techniquesuch as radical polymerization, and the resulting mixture oflow-molecular-weight compounds and high-molecular-weight compounds maybe used.

[0124] Examples of the above-described compound having polymerizabledouble bond include compounds obtained by oxidizing norbornyldi(mono)ene, tricyclodeca (mono)diene or tetracyclodeca (mono)diene tointroduce >C═O or —C(═O)—O— into at least one of the aliphatic rings.

[0125] Further, it is preferable that the above-described compoundcontaining polymerizable double bond be an alcohol or an ester compoundof a carboxylic acid. This is because such a compound is readilypolymerizable.

[0126] Furthermore, it is desirable that the above-described compoundhaving polymerizable double bond be an acrylic or methacrylic estercompound. This is because such a compound has high polymerizability andcan be polymerized at any composition ratio. It is more preferable thatadamantane, tricyclodecane, tetracyclodecane or hydronaphthaleneskeleton be contained in the side chain of the acrylic or methacrylicester compound.

[0127] It is particularly desirable to obtain a resin of the presentinvention by polymerizing, as a monomer, a compound represented by thefollowing general formula (III-1a) or (III-1b) because the resultingresin is excellent in dry-etching resistance and adhesion:

[0128] wherein R represents acryloyl or methacryloyl group.

[0129] In the compound represented by the general formula (1), carbonylgroup may be introduced to the 2-position.

[0130] Further, it is desirable to obtain a resin of the presentinvention by polymerizing, as a monomer, a compound represented by thefollowing general formula (III-2a) or (III-2b) because these compoundshave high polymerizability and can be polymerized at any compositionratio:

[0131] wherein R represents acryloyl or methacryloyl group, and R₁ andR₂ represent an alkyl group or a group decomposable by an acid. R₁ andR₂ may be partly cross-linked to form a cyclic compound. Moreover,adamantylidene group may be introduced to the 2-position.

[0132] Furthermore, it is desirable to obtain a resin of the presentinvention by polymerizing, as a monomer, a compound represented by thefollowing general formula (III-3a), (III-3b), or (III-3c) because theresulting resin is excellent in dry-etching resistance and adhesion:

[0133] wherein R represents acryloyl or methacryloyl group. The hydrogenatoms of compound (III-3a), (III-3b) and (III-3c) are able to besubstituted by other substituent.

[0134] Furthermore, it is desirable to obtain a resin of the presentinvention by polymerizing, as a monomer, a compound represented by thefollowing general formula (III-4) because this compound is highlypolymerizable and can be polymerized at any composition ratio:

[0135] wherein R₁ represents acryloyl or methacryloyl group.

[0136] [2] At least either one of a polyester resin or a polyacidanhydride resin is obtained by homopolymerizing the alicyclic compound(A) or (B) that is a monomer useful for synthesizing a resin accordingto the present invention, or, as its derivative, a compound containingtwo or more organic groups of at least one of hydroxyl group andcarboxyl group. Alternatively, the above compound and another compoundcontaining two or more groups of at least one of hydroxyl group andcarboxyl group may be subjected to condensation polymerization to obtaina desired resin.

[0137] [2]-1: A polyester resin can be obtained by the dehydrationcondensation of the alicyclic compound (A) or (B) that is a monomeruseful for synthesizing a resin according to the present invention, or,as its derivative, a compound having monohydroxy-monocarboxylic acidskeleton. Alternatively, a polyester resin may be obtained by thedehydration condensation of the alicyclic compound (A) or (B) that is amonomer useful for synthesizing a resin according to the presentinvention, or, as its derivative, a polyvalent carboxylic acid compoundcontaining two or more groups of at least one of hydroxyl group andcarboxyl group with a polyvalent alcoholic compound. Further, apolyester resin may also be obtained by the reaction between thealicyclic compound (A) or (B) that is useful for synthesizing a resinaccording to the present invention, or a derivative of the alicycliccompound that is a polyvalent alcohol having two or more groups of atleast one of hydroxyl group and carboxyl group and conjugated polycycliccondensed aromatic skeleton, and a polyvalent carboxylic acid. The abovepolyvalent carboxylic acid or polyvalent alcohol may be a mixture of twoor more compounds.

[0138] A polyester resin can also be obtained not only by theabove-described processes but also by any of widely-used processes forsynthesizing polyesters, for instance, by carrying out the ring-openingreaction of a lactone, the polymerization of a polyvalent carboxylicacid and a polyvalent alcohol by the ring-opening reaction of an acidanhydride, or the polymerization of a polyvalent carboxylic acid and apolyvalent epoxy compound in the case where a polyvalent carboxylic acidchloride and a polyvalent alcohol are subjected to desalting reaction bythe use of triethylamine or the like as a catalyst.

[0139] [2]-2: A polyacid anhydride resin can be obtained by the use ofthe alicyclic compound (A) or (B) that is useful for synthesizing aresin according to the present invention, or its derivative that is apolyvalent carboxylic acid having two or more groups of at least one ofhydroxyl group and carboxyl group; this monomer is singly subjected todehydration condensation. Alternatively, a polyacid anhydride resin canbe obtained by using the alicyclic compound (A) or (B), or a derivativethereof that is a polyvalent carboxylic acid having two or more groupsof at least one of hydroxyl group and carboxyl group, and a polyvalentcarboxylic acid chloride; these monomers are subjected to desaltingreaction by using triethylamine or like as a catalyst.

[0140] It is noted that the resin according to the present invention maycontain both polyester linkage and polyacid anhydride linkage at thesame time.

[0141] It is desirable to carry out dehydration condensation between apart of or all of >C═O contained in the resin of the present invention,and a compound having active methylene. By doing so, it is possible tofurther impart, to the resin, adhesion and the property of beingdecomposed by an acid.

[0142] The above-described compound having active methylene hereindenotes, for instance, those compounds having electron-attractingsubstituents on both sides of methylene. Examples of electron-attractinggroups include carbonyl group, carboxyl group, esters of carbonyl orcarboxyl groups, sulfonyl group, sulfonate group, cyano group, andhalogen atoms. Of these, malonic acid derivatives represented by thefollowing general formula (5) are desirable from the viewpoints ofadhesion, resolution and developability:

R₃O(CO)CH₂(CO)OR₄  (5)

[0143] wherein R₃ and R₄, which may be the same or different, representan alkyl group, or a group that can be decomposed by an acid. Further,R₃ and R₄ may be partly combined with each other to form a cycliccompound. In particular, when R₃ and R₄ are tert-butyl group, or whenthe compound having active methylene is a meldrum compound, the propertyof being decomposed by an acid, and solubility are improved,respectively.

[0144] In the present invention, it is preferable to incorporate thecomponents so that the amount of the alicyclic structure into whichdouble bond formed by condensation with active methylene has beenintroduced will be 10% by weight or more of the solid matter of theresist. When this amount is less than 10% by weight, it is difficult toform, by alkali development, a resist pattern excellent in bothresolution and adhesion. In addition, the resulting resist pattern tendsto have impaired dry-etching resistance. On the other hand, when theabove amount is made more than 90%, the transparency is lowered.

[0145] It is preferable to make the average molecular weight of theresin according to the present invention, calculated in terms ofpolystyrene, from 500 to 500,000. A resin having an average molecularweight of less than 500 is unfavorable for forming a resist film havingsufficiently high mechanical strength. On the contrary, when the averagemolecular weight of the polymer compound is in excess of 500,000, it isdifficult to form a resist pattern excellent in resolution. The resincomponent of a resist composition is, in general, a mixture consistingof components having different molecular weights. The resin according tothe present invention reveals its effects even when it has a lowmolecular weight. For example, even a resin containing components havingaverage molecular weights of 500 to 1,000 is prevented from beingdissolved unevenly, so that such a resin is also desirable. Moreover, inthis case, even if many monomers are remaining in the resin, it isacceptable as long as the resin can form a film without causing anyproblem.

[0146] [Structure Common to Resist Resins I, II and III]

[0147] A resin according to the present invention can be obtained bycopolymerizing the monomer and any of various vinyl compounds. Examplesof useful vinyl compounds include methyl acrylate, methyl methacrylate,alpha-chloroacrylate, cyanoacrylate, trifluoromethyl acrylate,alpha-methylstyrene, trimethylsilyl methacrylate, trimethylsilylalpha-chloroacrylate, trimethylsilylmethyl alpha-chloroacrylate, maleicanhydride, tetrahydropyranyl methacrylate, tetrahydropyranylalpha-chloroacrylate, t-butyl methacrylate, t-butylalpha-chloroacrylate, butadiene, glycidyl methacrylate, isobornylmethacryate, menthyl methacrylate, norbornyl methacrylate, adamantylmethacrylate and allyl methacrylate.

[0148] Moreover, when the control of the alkali-solubility of the resinand the improvement in adhesion between the resist and a substrate aretaken into consideration, it is preferable to copolymerize the monomerand acrylic acid, maleic anhydride, an ester substitution product ofacrylic acid or maleic anhydride, or an ankali-soluble compound such asvinyl phenol, vinyl naphthol, naphthol oxymethacrylate or SO₂. It isalso possible to copolymerize the monomer with a compound obtained byprotecting the alkali-soluble group of any of the above alkali-solublecompounds by a dissolution-preventive group (a group decomposable by anacid) having the ability of preventing dissolution.

[0149] It is preferable to introduce a dissolution-preventive group (asoluble group decomposable by an acid) into the molecule of a resinaccording to the present invention because the resulting resin hasimproved resolution. A dissolution-preventive group can be introducedinto a resin by using a monomer compound having thedissolution-preventive group when the resin is synthesized.

[0150] A cyclic tertiary ester group having a lactone, or a substituenthaving acid anhydride structure formed with a bridged-bond-containingalicyclic compound having a carboxylic acid acts as a soluble groupdecomposable by an acid. Therefore, such a group can conveniently beused as the dissolution-preventive group.

[0151] Examples of dissolution-preventive groups include the following:esters such as t-butyl ester, isopropyl ester, ethyl ester, methyl esterand benzyl ester; ethers such as tetrahydropyranyl ether; alkoxycarbonates such as t-butoxy carbonate, methoxy carbonate and ethoxycarbonate; silyl ethers such as trimethylsilyl ether, triethylsilylether and triphenylsilyl ether; esters such as isopropyl ester,tetrahydropyranyl ester, tetrahydrofuranyl ester, methoxyethoxy methylester, 2-trimethylsilylethoxymethyl ester, 3-oxocyclohexyl ester,isobornyl ester, trimethylsilyl ester, triethylsilyl ester,isopropyldimethylsilyl ester, di-t-butylmethylsilyl ester, oxazole,2-alkyl-1,3-oxazoline, 4-alkyl-5-oxo-1,3-oxazoline and5-alkyl-4-oxy-1,3-dioxolane; ethers such as t-butoxycarbonyl ether,t-butoxy-methyl ether, 4-pentenyloxymethyl ether, tetrahydropyranylether, tetrahydro-thiopyranyl ether, 3-bromotetrahydropyranyl ether,1-methoxycyclohexyl ether, 4-methoxytetrahydropyranyl ether,4-methoxytetrahydrothiopyranyl ether, 1,4-dioxane-2-yl ether,tetrahydrofuranyl ether, tetrahydrothiofuranyl ether,2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ylether, t-butyl ether, trimethylsilyl ether, triethylsilyl ether,triisopropylsilyl ether, dimethylisopropylsilyl ether,diethylisopropylsilyl ether, dimethylsesquisilyl ether andt-butyldimethylsilyl ether; acetals such as methylene acetal, ethylideneacetal and 2,2,2-trichloroethylidene acetal; ketals such as1-t-butylethylidene ketal, isopropylidene ketal (acetonide),cyclopentylidene ketal, cyclohexylidene ketal and cycloheptylideneketal; cyclic orthoesters such as methoxymethylene acetal,ethoxymethylene acetal, dimethoxymethylene orthoester,1-methoxyethylidene orthoester, 1-ethoxyethylidene orthoester,1,2-dimethoxyethylidene orthoester, 1-N,N-dimethylaminoethylideneorthoester and 2-oxacyclopentylidene orthoester; silyl ketene acetalssuch as trimethylsilylsilyl ketene acetal, triethylsilyl ketene acetaland t-butyldimethylsilyl ketene acetal; silyl ethers such asdi-t-butylsilyl ether, 1,3-1′, 1′, 3′, 3′-tetraisopropyldisiloxanylideneether and tetra-t-butoxy-disiloxane-1,3-diylidene ether; acyclic acetalsand ketals such as dimethyl acetal, dimethyl ketal,bis-2,2,2-trichloroethyl acetal, bis-2,2,2-trichloroethyl ketal,diacetyl acetal and diacetyl ketal; cyclic acetals and ketals such as1,3-dioxane, 5-methylene-1,3-dioxane, 5,5,-dibromo-1,3-dioxane,1,3-dioxolane, 4-bromomethyl-1,3-dioxolane, 4-3′-butenyl-1,3-dioxolaneand 4,5-dimethoxymethyl-1,3-dioxolane; cyanohydrins such asO-trimethylsilyl cyanohydrin, O-1-ethoxyethyl cyanohydrin andO-tetrahydropyranyl cyanohydrin; and leaving alicyclic skeletons such astertiary alicylic esters having alkyl groups.

[0152] It is preferable to make the percentage of thedissolution-preventive group approximately 35 to 65 mol % of the resin.This value is considerably greater than the percentage of adissolution-preventive group introduced to a conventional acrylicpolymer. For this reason, the resin of the invention has highdissolution contrast as compared with conventional acrylic resists.Moreover, a pattern formed by using the resin of the present inventioncan be developed with high resolution by a standard developer such as a2.38% aqueous solution of tetramethylammonium hydroxide (TMAH).

[0153] The resin according to the present invention may contain in itsmolecule a dissolution-preventive group and an alkali-soluble group atthe same time. Such a resin can show the two functions ofalkali-solubility and dissolution-preventing properties.

[0154] Examples of alkali-soluble groups include carboxyl group andphenolic hydroxyl group.

[0155] In this case, it is preferable to make the percentage of thedissolution-preventive group approximately 10 to 80 mol % of the resin.When this percentage is less than 10 mol %, the dissolution-preventingfunction cannot be revealed, and the unexposed area is also dissolved.It is thus impossible to attain the resolution of a pattern. On theother hand, when the above percentage is in excess of 80 mol %, theresin has extremely decreased adhesion, so that it is difficult to forma pattern. Moreover, the resist composition shows extremely highhydrophobicity and repels a developer, so that a pattern cannot beformed.

[0156] Further, in this case, the percentage of the alkali-soluble groupin the resin be so made that it will be 20 mol % or more in the areathat will be removed by development to be conducted after exposure/PEB(post exposure bake). When the percentage of the alkali-soluble group inthis area is made less than 20 mol %, the alkali developability becomesworse.

[0157] In the case where one alicyclic unit contains both adissolution-preventive group, and a polar group such as hydroxyl groupthat can improve adhesion, the above-described problem of adhesion isnot brought about. Therefore, in this case, it is possible to introducea dissolution-preventive group to an extent of 80 mol % or more.

[0158] In the resist composition of the present invention, it isdesirable that not only the resin but also a part of the structure of anadditive (dissolution-preventive agent), which will be described later,has the above-described group decomposable by an acid, thealkali-soluble group contained in this group being protected.

[0159] When a water-soluble compound is polymerized to obtain a resinaccording to the present invention, the resulting resin has improvedalkali-solubility. However, such a resin requires the use of a thindeveloper, so that the use of a water-soluble compound is undesirable.In the resin according to the present invention, it is preferable thatthe proportion of a vinyl compound having high water-solubility of morethan 0.1 g/g water is as low as possible, and it is most preferable thatthe resin does not contain such a compound. The proportion of a compoundwhose water-solubility is in excess of 0.1 g/g water is at most 0 to 20%by weight of the polymer.

[0160] To make a resin according to the present invention bypolymerization, it is preferable to use a compound having no molecularskeleton whose light absorption in short-wavelength ranges is high, suchas benzene nucleus, from the viewpoint of the transparency of theresulting resist against short-wavelength light. Specifically, it isdesirable that the absorbance of the resin against light having awavelength of 193 nm be 4 or less per 1 micrometer.

[0161] <Photo Acid Generator>

[0162] Examples of photo acid generators useful for resist compositionsof the present invention include the following compounds: aryl oniumsalts, naphthoquinonediazide compounds, diazonium salts, sulfonatecompounds, sulfonium compounds, sulfamide compounds, iodonium compoundsand sulfonyldiazomethane compounds. Specific examples of these compoundsinclude triphenylsulfonium triflate, diphenyliodonium triflate,2,3,4,4-tetrahydroxy-benzophenone-4-naphthoquinonediazidesulfonate,4-N-phenylamino-2-methoxyphenyldiazoniumsulfate,4-N-phenylamino-2-methoxyphenyldiazonium p-ethylphenylsulfate,4-N-phenylamino-2-methoxyphenyldiazonium 2-naphthylsulfate,4-N-phenylamino-2-methoxyphenyldiazoniumphenylsulfate,2,5-diethoxy-4-N-4′-methoxyphenylcarbonylphenyldiazonium3-carboxy-4-hydroxyphenyl sulfate, 2-methoxy-4-N-phenylphenyldiazonium3-carboxy-4-hydroxyphenylsulfate, diphenylsulfonylmethane,diphenylsulfonyldiazomethane, diphenyldisulfone,alpha-methylbenzointosylate, pyrogallol trimesylate, benzointosylate,MPI-103 (manufactured by Midori Kagaku Co., Ltd., Japan, CAS No.87709-41-9), BDS-105 (manufactured by Midori Kagaku Co., Ltd., CAS No.145612-664), NDS-103 (manufactured by Midori Kagaku Co., Ltd., CAS No.110098-97-0), MDS-203 (manufactured by Midori Kagaku Co., Ltd., CAS No.127855-15-5), Pyrogallol tritosylate (manufactured by Midori Kagaku Co.,Ltd., CAS No. 20032-64-8), DTS-102 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 75482-18-7), DTS-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 71449-78-0), MDS-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No.127279-74-7), MDS-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 116808-67-4), MDS-205 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 81416-37-7), BMS-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 149934-68-9), TMS-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 127820-386), NB-101 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 20444-09-1), NB-201 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 4450-68-4), DNB-101 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 114719-51-6), DNB-102 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 131509-55-2), DNB-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 132898-35-2), DNB-104 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 132898-363), DNB-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 132898-37-4), DAM-101 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 1886-74-4), DAM-102 (manufactured by Midori Kagaku Co.,Ltd., CAS No.28343-24-0), DAM-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 14159-45-6), DAM-104 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 130290-80-1), (manufactured by Midori Kagaku Co., Ltd.,CAS No. 130290-82-3), DAM-201 (manufactured by Midori Kagaku Co., Ltd.,CAS No. 28322-50-1), CMS-105 (manufactured by Midori Kagaku Co., Ltd.),DAM-301 (manufactured by Midori Kagaku Co., Ltd., CAS No. 138529-81-4),SI-105 (manufactured by Midori Kagaku Co., Ltd., CAS No. 34694-40-7),NDI-105 (manufactured by Midori Kagaku Co., Ltd., CAS No. 133710-62-0),and EPI-105 (manufactured by Midori Kagaku Co., Ltd., CAS No.135133-12-9). Moreover, the following compounds may also be used.

[0163] wherein C₁ and C₂ form single bond or double bond, R₁₀ ishydrogen atom, fluorine atom, or an alkyl or aryl group which may besubstituted with fluorine atom, and R₁₁ and R₁₂, which may be the sameor different, respectively represent a monovalent organic group, and maybe combined with each other to form a cyclic structure.

[0164] wherein Z represents an alkyl group.

[0165] Of the above-enumerated photo acid generators, conjugatedpolycyclic aromatic compounds having naphthalene or dibenzothiopheneskeleton, such as aryl onium salts, sulfonate compounds, sulfonylcompounds and sulfamide compounds are advantageous from the viewpointsof transparency against short-wavelength light, and of heat resistance.Specifically, the following compounds are preferred: sulfonyl orsulfonate compounds having naphthalene, pentalene, indene, azulene,heptalene, biphenylene, as-indacene, s-indacene, acenaphthylene,fluorene, phenalene, phenanthrene, anthracene, fluorantene,acephenanthrylene, aceanthrylene, triphenylene, pyrene, chrysene,naphthacene, pleiadene, picene, perylene, pentaphene, pentacene,tetraphenylene, hexaphene, hexacene, rubicene, coronene, trinaphthylene,heptaphene, heptacene, pyranthrene, ovalene, dibenzophenanthrene,benz[a]anthracene, dibenzo[a,j]anthracene, indeno[1,2-a]indene,anthra[2,1a]naphthacene or 1H-benzo[a]cyclopent[j]anthracene ring;4-quinonediazide compounds having naphthalene, pentalene, indene,azulene, heptalene, biphenylene, as-indacene, s-indacene,acenaphthylene, fluorene, phenalene, phenanthrene, anthracene,fluorantene, acephenanthrylene, aceanthrylene, triphenylene, pyrene,chrysene, naphthacene, pleiadene, picene, perylene, pentaphene,pentacene, tetraphenylene, hexaphene, hexacene, rubicene, coronene,trinaphthylene, heptaphene, heptacene, pyranthrene, ovalene,dibenzophenanthrene, benz[a]anthracene, dibenzo[a,j]anthracene,indeno[1,2-a]indene, anthra[2,1a]naphthacene or1H-benzo[a]cyclopent[j]anthracene ring; and salts with triflates ofsulfoniums or iodoniums having, as side chain, naphthalene, pentalene,indene, azulene, heptalene, biphenylene, as-indacene, s-indacene,acenaphthylene, fluorene, phenalene, phenanthrene, anthracene,fluorantene, acephenanthrylene, aceanthrylene, triphenylene, pyrene,chrysene, naphthacene, pleiadene, picene, perylene, pentaphene,pentacene, tetraphenylene, hexaphene, hexacene, rubicene, coronene,trinaphthylene, heptaphene, heptacene, pyranthrene, ovalene,dibenzophenanthrene, benz[a]anthracene, dibenzo[a,j]anthracene,indeno[1,2-a]indene, anthra[2,1a]naphthacene or1H-benzo[a]cyclopent[j]anthracene ring In particular, sulfonyl orsulfonate compounds having naphthalene or anthracene ring;4-quinonediazide compounds having naphthalene or anthracene ring towhich hydroxyl group has been introduced; and salts with triflates ofsulfoniums or iodoniums having as side chain naphthalene or anthracenering.

[0166] Of these photo acid generators, triphenylsulfonium triflate,diphenyliodonium triflate, trinaphthylsulfonium triflate,dinaphthyliodonium triflate, dinaphthylsulfonyl methane, NAT-105(manufactured by Midori Kagaku Co., Ltd., CAS No. 137867-61-9), NAT-103(manufactured by Midori Kagaku Co., Ltd., CAS. No. 131582-008), NAI-105(manufactured by Midori Kagaku Co., Ltd., CAS No. 85342-62-7), TAZ-106(manufactured by Midori Kagaku Co., Ltd., CAS No. 69432-40-2), NDS-105(manufactured by Midori Kagaku Co., Ltd.), PI-105 (manufactured byMidori Kagaku Co., Ltd., CAS No. 41580-58-9), s-alkylateddibenzothiophene triflate, and s-fluoroalkylated dibenzothiophenetriflate (manufactured by Daikin Industries, Ltd., Japan) are preferablyused. Of these compounds, triphenylsulfonium triflate,trinaphthylsulfonium triflate, dinaphthyliodonium triflate,dinaphthylsulfonyl methane, NAT-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 137867-61-9), NDI-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 133710-62-0), and NAI-105 (manufactured by Midori KagakuCo., Ltd., CAS No. 85342-62-7) are particularly preferred.

[0167] In the resist composition of the present invention, the amount ofthe photo acid generator to be incorporated is from 0.001 to 50% byweight, more preferably from 0.01 to 40% by weight, most preferably from0.1 to 20% by weight of the total amount of the other solid components.When this amount is less than 0.001% by weight, it is difficult to forma resist pattern at high sensitivity. On the other hand, when thisamount is in excess of 50% by weight, the resulting resist film may haveimpaired mechanical strength.

[0168] <Other Components>

[0169] The resist composition of the present invention may furthercomprise dissolution-preventive agents, alkali-soluble resins, andresinous compounds whose alkali-solubility is increased when irradiated.

[0170] Dissolution-preventive agents will be described hereinafter.

[0171] A resin according to the present invention, which is insoluble inalkalis, becomes alkali-soluble by being decomposed by an acid catalystthat is generated from the photo acid generator incorporated into theresin when light is applied to the generator. It is therefore notessential to introduce a dissolution-preventive group into the resin, orto add a dissolution-preventive agent to the resist composition.However, in order to obtain a great difference in dissolution ratebetween exposed area and unexposed area, it is preferable to introduce adissolution-preventive group into the resin, or to add adissolution-preventive agent to the resin composition.

[0172] Among the compounds described in, for example, U.S. Pat. Nos.4,491,628 and 4,603,101, and Japanese Patent Laid-Open PatentPublication No. 27829/1988, those ones whose aromatic rings are thecondensed polycyclic aromatic rings can be used asdissolution-preventive compounds which can serve as thedissolution-preventive agents. Alternatively, those compounds containingcondensed polycyclic aromatic ring skeleton having carboxylic acids orphenolic hydroxyl groups can be used if a part of or all of the hydroxylends are substituted with protective groups decomposable by an acid.

[0173] Examples of the above protective groups include tert-butyl ester,tert-butyl carbonate, tetrahydropyranyl group and acetal group.

[0174] Specific examples of such compounds include tert-butyl carbonatesof naphthalene, anthracene, and polyhydroxy compounds, tert-butylcarbonate of naphthol phthalein, quinazarine, quinizarine, tert-butylcarbonates of naphthol novolak resins.

[0175] The amount of this compound to be incorporated into the resistcomposition is desirably at least 3% by weight and less than 40% byweight of the polymer. When the amount of this compound to be added ismade less than 3% by weight, the effects of the compound cannot beobtained, or the lowering of resolution is brought about. On thecontrary, when this amount is made more than 40% by weight, the coatingperformance or dissolution rate is drastically decreased. In general, itis more desirable that this amount be from 10 to 30% by weight.

[0176] In the case where the resist composition contains adissolution-preventive agent, the resin is not always necessary to havea dissolution-preventive group. In this case, the resin may be onecopolymerized with a vinyl compound having an alkali-soluble group, suchas methacrylic acid, capable of imparting alkali-solubility to thecopolymer. Examples of dissolution-preventive agents include compoundsdecomposable by an acid, which can sufficiently showdissolution-preventing ability in alkaline solutions and whosedecomposition products can produce, in alkaline solutions, —(C═O)O—,—OS(═O)₂— or —O—. Specific examples of these compounds includet-butoxycarbonyl ether, tetrahydropyranyl ether,3-bromotetrahydropyranyl ether, 1-methoxycyclohexyl ether,4-methoxy-tetrahydropyranyl ether, 1,4-dioxane-2-yl ether,tetrahydrofuranyl ether,2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ylether, t-butyl ether, trimethylsilyl ether, triethylsilyl ether,triisopropylsilyl ether, dimethylisopropylsilyl ether,diethylisopropylsilyl ether, dimethylsesquisilyl ether ort-butyldimethylsilyl ether of phenolic compounds, meldrum acidderivatives, and the like. Of these, those compounds obtained byprotecting the hydroxyl group of phenolic compounds by t-butoxycarbonyl,t-butoxycarbonylmethyl, trimethylsilyl, t-butyldimethylsilyl ortetrahydropyranyl group, those compounds obtained by adding meldrum acidto naphthaldehyde, and those compounds obtained by adding meldrum acidto aldehydes having alicyclic structure are preferred.

[0177] Moreover, the dissolution-preventive agent may be isopropylester, tetrahydropyranyl ester, tetrahydrofuranyl ester,methoxyethoxymethyl ester, 2-trimethylsilylethoxymethyl ester, t-butylester, trimethylsilyl ester, triethylsilyl ester, t-butyldimethylsilylester, isopropyldimethylsilyl ester, di-t-butylmethylsilyl ester,oxazole, 2-alkyl-1,3-oxazoline, 4-alkyl-5-oxo-1,3-oxazoline,5-alkyl-4-oxo-1,3-dioxolane or the like of polyvalent carboxylic acids.In addition, there can also be mentioned compounds represented by thefollowing formula.

[0178] Of these dissolution-preventive agents, conjugated polycyclicaromatic compounds are preferable in the present invention because thesecompounds are excellent in transparency against short-wavelength light.Light absorption bands are shifted to shorter wavelength regions inthese compounds due to the stabilization of conjugation of pi electrons.Therefore, in the present invention, it is possible to obtain a resisthaving excellent transparency against short-wavelength light andsufficiently high heat resistance by using especially a conjugatedphenolic aromatic compound as the dissolution-preventive agent.

[0179] For the alkali-soluble resins included in the above-describedother components of the resist composition of the present invention, anyresin can be used as long as it is basically alkali-soluble. Preferableexamples of such resins include those ones useful for known ArF resists,and they may have the functions of chemically amplified resists.

[0180] Further, the resist composition of the present invention may forma negative image when a resin having acid anhydride structure isprocessed as the resin component at a high temperature, or when hydroxylgroup is attached to the specific tertiary carbon atom of the resincomponent, such hydroxyl group being readily underwent dehydrationcondensation reaction by an acid catalyst. By taking advantage of thisaction, a negative image may be formed.

[0181] The resist composition of the present invention is, in general,prepared as a varnish by dissolving a resin component, a photo acidgenerator, a dissolution-preventive agent, a cross-linking agent, analkali-soluble resin and the like in an organic solvent, and filteringthe solution. The resist for alkali development according to the presentinvention may further contain the following agents and compounds: otherpolymers such as epoxy resins, polymethyl methacrylate, polymethylacrylate, polymethyl methacrylate, propylene oxide-ethylene oxidecopolymers and polystyrene, amine compounds useful for improvingenvironmental resistance, basic compounds such as pyridine derivatives,surface active agents useful as film modifiers, andreflection-preventive agents.

[0182] Examples of the organic solvent herein used include ketonesolvents such as cyclohexane, acetone, methyl ethyl ketone and methylisobutyl ketone, cellosolve solvents such as methyl cellosolve, methylcellosolve acetate, ethyl cellosolve acetate and butyl cellosolveacetate, ester solvents such as ethyl acetate, butyl acetate, isoamylacetate and gamma-butyrolactone, glycol solvents such as propyleneglycol monomethyl ether acetate, dimethyl sulfoxide, andnitrogen-containing solvents such as hexamethylphosphoric triamidedimethylformamide and N-methylpyrrolidone. Besides the above solvents,solvent mixtures obtained by adding dimethyl sulfoxide,dimethylformaldehyde, N-methylpyrrodinone or the like to theabove-enumerated solvents in order to improve the solubility may also beused. Further, propionic acid derivatives such as methylmethylpropionate, lactic esters such as ethyl lactate, PGMEA (propyleneglycol monomethyl ether acetate) and the like do not have high toxicity,so that they can also be favorably used. Of these, PGMEA and ethyllactate are particularly preferred because they are highly soluble inthe resins of the present invention.

[0183] In the present invention, these solvents may be used eithersingly or in combination of two or more members. Moreover, the solventmay further contain an aliphatic alcohol such as isopropyl alcohol,ethyl alcohol, methyl alcohol, butyl alcohol, n-butyl alcohol, s-butylalcohol, t-butyl alcohol or isobutyl alcohol, or an aromatic solventsuch as toluene or xylene. When the resist composition of the presentinvention has acid anhydride structure, it shows high reactivity if thesolvent contains hydroxyl group, and thus loses its stability. In thiscase, therefore, the solvent is desirably one having no OH group.

[0184] Next, a pattern forming process using a resist composition of thepresent invention will be described hereinafter by referring to the casewhere the resist is a chemically amplified positive resist. First ofall, a varnish prepared by dissolving the resist in an organic solventin the above-described manner is coated onto a predetermined substrateby means of spin coating or dipping. Thereafter, the varnish coated ontothe substrate is dried at a temperature of 150° C. or lower, preferablyfrom 70 to 120° C. to form a resist film. Examples of the substrateuseful herein include silicon wafers, silicon wafers whose surfaces areprovided with various insulating films, electrodes and lines, blankmasks, semiconductor wafers made from compounds belonging to the groupsIII to V such as GaAs or AlGaAs, masks on which chrome or chrome oxideis vacuum-deposited, aluminum-deposited substrates, BPSG-coatedsubstrates, PSG-coated substrates, BSG-coated substrates, SOG-coatedsubstrates, and carbon-film-sputtered substrates.

[0185] Subsequently, actinic radiation is applied to the resist filmthrough a predetermined mask pattern, or directly scanned on the surfaceof the resist film, thereby exposing the resist film to light. Asmentioned previously, the resist of the present invention for alkalidevelopment has excellent transparency against not only short-wavelengthlight but also light of wide wavelength regions. It is thereforepossible to use as the actinic radiation ultraviolet rays, X-rays, thei-, h-, or g-rays of a low-pressure mercury vapor lamp, light emitted bya xenon lamp, deep UV light such as KrF, ArF, or F₂ excimer laser light,synchrotron orbital radiation (SOR), electron beams (EB), gamma rays,ion beams or the like.

[0186] In particular, in the case of a chemically amplified resist, theresist film is subjected to baking treatment at a temperature ofapproximately 170° C. or lower by heating the resist film on a hot plateor in an oven, or by applying infrared light to the resist film.Thereafter, the resist film is developed by means of dipping or sprayingto selectively dissolve it in an alkaline solution, thereby removing theexposed area or unexposed area of the resist film to form a desiredresist pattern. Specific examples of the alkaline solution that can beused herein include aqueous organic alkaline solutions such as anaqueous tetramethylammonium hydroxide solution and an aqueous cholinesolution, aqueous inorganic alkaline solutions such as an aqueouspotassium hydroxide solution and an aqueous sodium hydroxide solution,and solutions obtained by adding alcohols, surface active agents or thelike to these solutions. It is preferable that the concentration of thealkaline solution be 15% by weight or less in order to obtain asufficient difference in dissolution rate between the exposed area andthe unexposed area.

[0187] The resist pattern thus formed by the use of the resistcomposition of the present invention is extremely excellent inresolution. For example, when dry etching is conducted by using thisresist pattern as an etching mask, an extremely fine pattern at aquarter micron level can be transferred to the bare substrate with highfidelity. The resist pattern herein obtained shows high dry-etchingresistance because, even when one of C—C bond in the alicyclic structurecontained in the polymer compound, base resin, is broken, the other bondcan remain.

[0188] Any step other than the above-described steps may be added to thepattern forming process of the present invention. For example, it ispossible to properly add the step of forming a planarizing layer as theground layer of the resist film, the step of pretreatment to be carriedout in order to improve the adhesion between the resist film and thesubstrate, the step of rinsing to be carried out after developing theresist film for removing the developer by using water or the like, andthe step of re-applying ultraviolet light before conducting dry etching.

EXAMPLES

[0189] The present invention will now be explained more specifically byreferring to the following examples.

Synthesis Example I-1

[0190] 6.0 g of 2-(3-carboxy-1-adamantyl)-2-propyl acrylate was mixedwith 20 g of tetrahydrofuran (THF). To this mixture was added 0.20 g ofazo-isobutyro-nitrile (AIBN), and the mixture was heated at 60° C. for35 hours with stirring. The reaction solution was added dropwise ton-hexane. The precipitate was collected by filtration, and dried toobtain a copolymer represented by the following chemical formula, havinga weight-average molecular weight (calculated in terms of styrene) ofapproximately 5,000.

Synthesis Example I-2

[0191] 50 mol % of 2-(3,7-dimethyl-4-adamantanon-1-yl)-2-propyl acrylateand 50 mol % of 3-(3-hydroxy-1-adamantyl)-3-pentyl acrylate, the totalamount being 6.0 g, were mixed with 20 g of THF. To this mixture wasadded 0.20 g of AIBN, and the mixture was heated at 60° C. for 35 hourswith stirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately5,000.

Synthesis Example I-3

[0192] 65 mol % of 1-(3-hydroxy-1-adamantyl)-1-propyl acrylate, 25 mol %of t-butyl acrylate and 10 mol % of methacrylic acid, the total amountbeing 6.0 g, were mixed with 20 g of THF. To this mixture was added 0.36g of AIBN, and the mixture was heated at 60° C. for 35 hours withstirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately8,000.

Synthesis Example I-4

[0193] 80 mol % of 3-(3-hydroxy-1-adamantyl)-3-pentyl acrylate and 20mol % of 4,6,6-trimethyl-2-oxepanon-4-yl acrylate, the total amountbeing 6.0 g, were mixed with 20 g of THF. To this mixture was added 0.20g of AIBN, and the mixture was heated at 60° C. for 35 hours withstirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately7,000.

Synthesis Example I-5

[0194] 60 mol % of 2-(3-hydroxy-1-adamantyl)-2-propyl acrylate, 30 mol %of 5-acryloyloxy-2-adamantanone, and 10 mol % of methacrylic acid, thetotal amount being 6.0 g, were mixed with 20 g of THF. To this mixturewas added 0.18 g of AIBN, and the mixture was heated at 60° C. for 35hours with stirring. The reaction solution was added dropwise ton-hexane. The precipitate was collected by filtration, and dried toobtain a copolymer represented by the following chemical formula, havinga weight-average molecular weight (calculated in terms of styrene) ofapproximately 7,000.

Synthesis Example I-6

[0195] 70 mol % of 2-(3-hydroxy-1-adamantyl)-2-propyl acrylate, 20 mol %of 2-vinyl naphthalene, and 10 mol % of methacrylic acid, the totalamount being 6.0 g, were mixed with 20 g of THF. To this mixture wasadded 0.18 g of AIBN, and the mixture was heated at 60° C. for 35 hourswith stirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately7,000.

Synthesis Example I-7

[0196] 50 mol % of 2-(3-hydroxy-1-adamantyl)-2-propyl acrylate, and 50mol % of maleic anhydride, the total amount being 6.0 g, were mixed with20 g of THF. To this mixture was added 0.18 g of AIBN, and the mixturewas heated at 75° C. for 24 hours with stirring. The reaction solutionwas added dropwise to methanol to coagulate the copolymer. The copolymerwas dissolved in THF again, and the solution was added dropwise ton-hexane. The precipitate was collected by filtration, and dried toobtain a copolymer represented by the following chemical formula, havinga weight-average molecular weight (calculated in terms of styrene) ofapproximately 4,000.

Synthesis Example I-8

[0197] 70 mol % of 2-(3,3-dimethtyl-3-hydroxy-1-adamantyl)-2-propylmethacrylate, and 30 mol % of tetrahydropyranyl methacrylate, the totalamount being 6.0 g, were mixed with 20 g of THF. To this mixture wasadded 0.18 g of AIBN, and the mixture was heated at 60° C. for 35 hourswith stirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately6,000.

Synthesis Example I-9

[0198] 60 mol % of2-(3-tetrahydropyranyloxycarbonyl-1-adamantyl)-2-propyl acrylate, and 40mol % of 1-methacryloyloxy-3-hydroxyadamantane, the total amount being6.0 g, were mixed with 20 g of THF. To this mixture was added 0.18 g ofAIBN, and the mixture was heated at 60° C. for 35 hours with stirring.The reaction solution was added dropwise to n-hexane. The precipitatewas collected by filtration, and dried to obtain a copolymer representedby the following chemical formula, having a weight-average molecularweight (calculated in terms of styrene) of approximately 6,000.

Synthesis Example I-10

[0199] 70 mol % of carboxytricyclododecyl acrylate, and 30 mol % ofethoxyethoxycarbonyltricyclododecyl methacrylate, the total amount being6.0 g, were mixed with 20 g of THF. To this mixture was added 0.18 g ofAIBN, and the mixture was heated at 60° C. for 35 hours with stirring.The reaction solution was added dropwise to n-hexane. The precipitatewas collected by filtration, and dried to obtain a copolymer representedby the following chemical formula, having a weight-average molecularweight (calculated in terms of styrene) of approximately 15,000.

Synthesis Example I-11

[0200] 50 mol % of 2-adamantyl-2-propyl methacrylate, and 50 mol %mevalonic lactone methacrylate, the total amount being 6.0 g, were mixedwith 20 g of THF. To this mixture was added 0.18 g of AIBN, and themixture was heated at 60° C. for 35 hours with stirring. The reactionsolution was added dropwise to n-hexane. The precipitate was collectedby filtration, and dried to obtain a copolymer represented by thefollowing chemical formula, having a weight-average molecular weight(calculated in terms of styrene) of approximately 11,000.

Example I-1

[0201] To the polymer obtained in Synthesis Example I-1 was addedtriphenylsulfonium triflate in an amount of 1% by weight of the polymer.This composition was made into a 10 wt % ethyl lactate solution. Afterfiltering through a 0.2 micron membrane filter, the solution wasspin-coated onto a silicon wafer which had been treated with hexamethyldisilazane, and pre-baked at 120° C. for 90 seconds to form a film witha thickness of 0.2 micrometers. This film was exposed to ArF excimerlaser (NA=0.55) light. Thereafter, the wafer was baked at 110° C. for 60seconds, and then developed by a 2.38% aqueous solution oftetramethylammonium hydroxide for 60 seconds. As a result, theresolution with an L/S of 0.25 micrometers was attained at an exposureenergy of 3.5 mJ/cm².

[0202] According to optical-microscopic observations, no peeling of thepattern was confirmed, and the adhesion between the film and thesubstrate was also found to be excellent. Moreover, any residue calledscum which tends to be formed when development is conducted was notobserved.

Examples I-2 to I-9 and Comparative Examples I-1 and I-2

[0203] To the respective polymers obtained in Synthesis Examples 2 to 9and Synthesis Examples 10 and 11, triphenylsulfonium triflate was addedin an amount of 1% by weight of the polymer. The compositions obtainedwere respectively dissolved in proper solvents. By using thesesolutions, pattern formation was conducted in the same manner as inExample I-1. The results are shown in Table I-1. TABLE I-1 Post ExposureDevelopment Exposure Baking TMAH Adhesion Energy Temp. Time conc. TimeDevelopability to (mJ/cm²) (° C.) (sec) (wt %) (sec) (μmL/S) substrateScum Ex. I-1 3.5 110 60 2.38 60 0.25 Not formed Ex. I-2 3.6 110 60 2.3855 0.24 Not formed Ex. I-3 8.8 110 60 2.38 40 0.17 Not formed Ex. I-44.7 110 60 2.38 45 0.15 Not formed Ex. I-5 6.8 110 60 2.38 40 0.17 Notformed Ex. I-6 7.8 110 60 2.38 50 0.17 Not formed Ex. I-7 4.5 110 601.15 40 0.15 Not formed Ex. I-8 3.9 110 60 2.38 40 0.16 Not formed Ex.I-9 4.7 110 60 2.38 90 0.15 Not formed Comp. Ex. 11.0 70 60 2.38 60 0.16Slightly I-1 formed Comp. Ex. 5.5 110 60 2.38 90 0.16 X Formed I-2

[0204] As is clear from the data shown in the above table, the resistcompositions of the present invention were superior to that ofComparative Example I-i in sensitivity and developability. The resist ofComparative Example I-2 was poor in adhesion to the substrate, and afine pattern could not be formed unless a ground film was provided onthe substrate beforehand. Moreover, this resist formed scum, like theresist of Comparative Example I-1, when development was conducted. Theresist compositions of the present invention were also excellent in thispoint. Production Example 1 of Semiconductor Device

[0205] By referring now to the accompanying drawings, a method forproducing semiconductor devices, using the resist compositions andpattern forming process of the present invention will now be explained.

[0206]FIG. 1 is a cross-sectional view showing one example of a processfor producing a semiconductor chip by using the resist composition ofthe present invention.

[0207] As shown in FIG. 1(a), a silicon oxide film with a thickness ofapproximately 0.8 micrometers was formed as an etching film on a siliconsemiconductor substrate 1 by CVD. On top of this film, a resist film 3with a thickness of approximately 0.3 micrometers, comprising the resistcomposition of Example I-1 was formed.

[0208] This resist film 3 was patterned by the above-described method toform a pattern composed of open holes, each having a diameter of 0.3micrometers. The resist pattern 3 a obtained was heated at 130° C. for30 minutes in nitrogen atmosphere. The silicon oxide etching film 2 wasselectively etched by RIE using CF₄ gas, and, as an etching mask, theabove-obtained resist pattern 3A to conduct pattern transfer as shown inFIG. 1(b).

[0209] Finally, the resist pattern 3A was carbonized and removed by O₂plasma to obtain the silicon oxide film 2 having fine open holes 6 asshown in FIG. 1(c). The diameter of the fine open hole 6 formed in thesilicon oxide film 2 is 0.32 micrometers, and the scattering in thethicknesses of the film was below 2%. Production Example 2 ofSemiconductor Device

[0210] As shown in FIG. 2(a), a silicon oxide film 2 with a thickness of0.8 micrometers was formed on a semiconductor substrate 1 by CVD. In thesemiconductor substrate 1, MOSFET, a diode and other elements (not shownin the figure), for example, had been formed in advance. Subsequently, alower wiring layer 10 composed of Al—Si—Cu, having a thickness ofapproximately 0.3 micrometers, and an interlayer insulating layer 7 madefrom SiO₂, having a thickness of 0.5 micrometers were formed. On theselayers was formed an upper wiring layer 11 composed of Al—Si—Cu, havinga thickness of approximately 0.3 micrometers. At this time, a step ofapproximately 0.2 micrometers was formed in the upper wiring layer. Aresist film 3 with a thickness of 0.3 micrometers, comprising the resistcomposition was further formed on the upper wiring layer 11 in the samemanner as in Production Example 1 of Semiconductor Device.

[0211] This resist film was patterned in the same manner as inProduction Example 1 of Semiconductor Device to form a resist pattern.By using this pattern as an etching mask, the upper wiring layer 11 wasremoved by RIE, using a chlorine gas such as CC1 ₄ to obtain an upperwiring layer 11A as shown in FIG. 2(b).

[0212] Finally, the resist pattern 3A was carbonated and removed by O₂plasma to obtain two-layered wiring as shown in FIG. 2(c).

Production Example 3 of Semiconductor Device

[0213]FIG. 3 is a cross-sectional view showing a case where the presentinvention is applied to the formation of Au wiring.

[0214] First of all, a silicon oxide film 2 with a thickness ofapproximately 0.8 micrometers was formed on a semiconductor substrate 1by CVD. In the semiconductor substrate 1, MOSFET, a diode and otherelements (not shown in the figure), for instance, had been formedbeforehand. Subsequently, on top of this silicon oxide film 2, atitanium-containing tungsten (Ti—W) film 12 with a thickness ofapproximately 0.2 micrometers, and a gold (Au) film 13 with a thicknessof approximately 0.1 micrometers were formed successively. A resist filmhaving a thickness of approximately 0.3 micrometers, containing the sameresist composition as in Production Example 1 of Semiconductor Devicewas further formed on the Au film.

[0215] This resist film 3 was patterned in the same manner as inProduction Example 1 of Semiconductor Device to form a resist pattern 3Aas shown in FIG. 3(b), thereby making a groove. By using the Ti—W film12 and Au film 13 bared at the bottom of the groove as electrodes, an Auplating film 14 with a thickness of 1 micrometer was formed in thegroove by electroplating.

[0216] Subsequently, the resist film 3A was carbonated and removed by O₂plasma to make the Au plating film 14 project from the Au film 13 asshown in FIG. 3(c). Finally, the bare Au film 13 was removed by ionmilling, and the bare Ti—W film 13 was removed by the use of a fluorinegas to form an Au wiring 20 as shown in FIG. 3(d).

Example II-1

[0217] 1-Acryloyl-3-hydroxyadamantane and tetrahydropyranyl methacrylatewere used as monomers. They were mixed with each other in one of themixing ratios shown in Table II-1, the total amount of the monomersbeing 0.05 mol. This mixture was dissolved in 20 g of THF. To thissolution was added 0.0125 mol of azobisbutyronitrile (AIBN) as apolymerization initiator. In argon atmosphere, the mixture was subjectedthree times to freezing deaeration at a temperature of liquid nitrogen,followed by reaction at 60° C. for 30 hours. To this reaction solutionwas added 2 ml of methanol to terminate the reaction. The reactionsolution was added dropwise to 250 g of hexane with stirring forreprecipitation. The solution was filtered through a glass filter, andthe solid matter collected was vacuum-dried at 60° C. for three days. Inthis manner, six different resins were obtained.

[0218] The molecular weights of the resins obtained, calculated in termsof polystyrene, were in the range of 3,500 to 8,000. The Mw/Mn ratioswere found to be from 1.7 to 1.9. The mixing ratio of the monomers ineach resin was determined by NMR. As a result, it was within ±2% of theratio of the monomers at the time when they were charged.

[0219] To 1.0 g of the respective resins obtained was added 0.05 g oftriphenylsulfonium triflate as a photo acid generator. The mixtures wererespectively dissolved in 4.2 g of ethyl lactate to obtain six differentResists 1 to 6.

[0220] These six resist solutions were respectively spin-coated ontosilicon wafers at 3,000 rpm for 30 seconds. Thereafter, the siliconwafers were subjected to pre-exposure bake on a hot plate at 120° C. for90 seconds. The thicknesses of the resist films were 0.5 micrometers.The resist films were exposed to ArF excimer laser light (wavelength 193nm) to form a line & space pattern. The apparatus used for the exposurewas an ArF exposure system (NA=0.55, delta=0.7) manufactured by NikonCorp., Japan.

[0221] The patterned resists were subjected to post-exposure bake at100° C. for 180 seconds, and then developed by a 2.38% aqueous solutionof tetramethylammonium hydroxide at 25° C. for 60 seconds. By this, theexposed area of each resist film was selectively dissolved and removed,and a positive pattern was formed. The sensitivities and degrees ofresolution of the resists are also shown in Table II-1. TABLE II-1Mixing Sensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) RemarksResist II-1 66:34 7.0 0.25 — Resist II-2 60:40 4.5 0.19 — Resist II-355:45 3.8 0.17 — Resist II-4 50:50 3.0 0.15 — Resist II-5 45:55 3.2 0.230.15 μmL/S when a protective film was used Resist II-6 40:60 3.4 0.300.15 μmL/S when a protective film was used

Example II-2

[0222] 0.02 mol of 1-acryloyl-3-hydroxyadamantane, monomer, washomopolymerized in the same manner as in Example I-1. The molecularweight of the homopolymer, calculated in terms of the polystyrene, was3,500, and the Mw/Mn was 1.9.

[0223] Patterning was conducted in the same manner as in Example II-1except that the photo acid generator used in Example II-1 was changed tonaphthylimide campharsulfonate and that the post-exposure bake wascarried out at 160° C. As a result, it was confirmed that it waspossible to form a pattern although the L/S was as large as 0.45micrometers at an exposure energy of 42 mJ/cm2. TABLE II-2 MixingSensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) Remarks Resist II-7— 42 0.45 —

Examples II-11 to II-15

[0224] Polymers were produced by the same method as in Example II-1except that the 1-acryloyl-3-hydroxyadamantane used in Example II-1 wasreplaced by 1-acryloyl-3-carboxyadamantan and that the mixing ratiosused in Example II-1 were changed to those shown in Table II-3. By usingthese polymers, resists were prepared in the same manner as in ExampleII-1. Patterning was conducted in the same manner as in Example II-1 bythe use of these resists. The results are shown in Table II-3. TABLEII-3 Mixing Sensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) RemarksResist II-11 55:45 2.9 0.20 — Resist II-12 50:50 2.7 0.18 — Resist II-1345:55 2.6 0.17 — Resist II-14 40:60 2.7 0.15 — Resist II-15 35:65 2.70.16 —

[0225] It is considered that why the optimum mixing ratios are differentfrom those in Example II-1 is due to difference in acidity. It can beknown that patterning can successfully be conducted by using theseresists.

Example II-4

[0226] A polymer was made in the same manner as in Example II-1 exceptthat a monomer mixture (molar ratio 1:1:2) of1-acryloyl-3-tert-butyloxycarbonyl adamantane,1-acryloyl-3-hydroxyadamantane and maleic anhydride was used instead ofthe monomers used in Example II-1. By the use of this polymer, a resistwas prepared in the same manner as in Example II-1. Patterning wasconducted in the same manner as in Example II-1 by using this resist. Asa result, it was confirmed that it was possible to form a pattern withan L/S of 0.17 micrometers at an exposure energy of 12 mJ/cm². Theresults are shown in Table II-4.

[0227] On the other hand, a polymer was made in the above-describedmanner by using a monomer mixture (molar ratio 1:1:2) of2-acryloyl-7-tert-butyloxy-carbonyltricyclodecane,2-acryloyl-7-hydroxymethyltricyclodecane, and maleic anhydride. A resistwas prepared in the same manner as in the above by using this polymer,and then evaluated. It was impossible to form a pattern at all due tocross-linking reaction. It can thus be known that the resin having thestructure according to the present invention shows notable effects whenit contains an acid anhydride. TABLE II-4 Mixing Sensitivity ResolutionResist Ratio (mJ/cm²) (μmL/S) Remarks Resist II-16 1:1:2 12 0.17 —

[0228] (“Mixing Ratio” denotes the molar ratio of1-acryloyl-3-tert-butyloxycarbonyl adamantane:1-acryloyl-3-hydroxyadamantane:maleic anhydride at the time when theywere charged.)

Example II-5

[0229] Polymers were produced in the manner as in Example II-1 exceptthat the 1-acryloyl-3-hydroxyadamantane used in Example II-1 wasreplaced with 1-acryloyl-3-tetrahydropyranylcarboxyadamantane and1-acryloyl-3-hydroxyadamantane and that the mixing ratios used inExample II-1 were changed to those shown in Table II-5. By the use ofthese polymers, resists were prepared in the same manner as in ExampleII-1. Patterning was conducted in the same manner as in Example II-1 byusing these resists. The results are shown in Table II-5. TABLE II-5Mixing Sensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) RemarksResist II-21 60:40 6.8 0.17 — Resist II-22 55:45 5.8 0.17 — Resist II-2350:50 5.6 0.16 — Resist II-24 45:55 5.4 0.18 — Resist II-25 40:60 5.90.19 —

[0230] (“Mixing Ratio” denotes the molar ratio of1-acryloyl-3-tetrahydropyranyl-carboxyadamantane to1-acryloyl-3-hydroxyadamantane at the time when they were charged.)

Example II-6

[0231] A mixture of 0.06 mol of Compound II-1 and 0.04 mol of CompoundII-2 was subjected to radical polymerization, using 0.01 mol of AIBN asa polymerization initiator to obtain Resin II-3 having a molecularweight of approximately 11,000. To 1.0 g of the resin obtained was added0.01 g of triphenylsulfonium triflate as a photo acid generator, and themixture was dissolved in 10 g of PGMEA. The resist solution thusobtained was spin-coated onto a silicon wafer at 3,000 rpm for 30seconds, and then subjected to pre-exposure bake on a hot plate at 120°C. for 90 seconds. The thickness of the resist film formed was 0.2micrometers. This resist film was exposed to ArF excimer laser light toform a line & space pattern. This was then subjected to post-exposurebake at 130° C. for 90 seconds, and developed by a 2.38% aqueous TMAHsolution at 25° C. for 60 seconds, thereby obtaining a positive patternwith an L/S of 0.15 micrometers. The sensitivity was 7.0 mJ/cm².

Example II-7

[0232] A mixture of 0.04 mol of Compound II-1 and 0.06 mol of CompoundII-4 was subjected to radical polymerization, using 0.01 mol of AIBN asa polymerization initiator to obtain Resin II-5 having a molecularweight of approximately 10,000. To 1.0 g of the resin obtained was added0.01 g of triphenylsulfonium triflate as a photo acid generator, and themixture was dissolved in 10 g of PGMEA. The resist solution thusobtained was spin-coated onto a silicon wafer at 3,000 rpm for 30seconds, and then subjected to pre-exposure bake on a hot plate at 120°C. for 90 seconds. The thickness of the resist film obtained was 0.2micrometers. This resist film was exposed to ArF excimer laser light toform a line & space pattern. This was then subjected to post-exposurebake at 110° C. for 90 seconds, and developed by a 2.38% aqueous TMAHsolution at 25° C. for 60 seconds, thereby obtaining a positive patternwith an L/S of 0.15 micrometers. The sensitivity was 30 mJ/cm².

Examples II-33-38

[0233] Polymer compounds II-12 to II-17 were obtained by radicallypolymerizing, as monomers, Compounds II-6 to II-11 and Compound II-2 or1-acryloyloxy-3-carboxyladamantane. The polymer compounds II-12 to II-17were respectively mixed with an acid generator TPS-105 (1 wt %), and themixtures were respectively dissolved in a PGMEA solution. Thesevarnishes obtained were respectively spin-coated onto silicon wafers.The films formed were exposed to light of 193 nm by using an ArF excimerlaser stepper, and baked at 110° C. for 5 minutes. The baked films werethen developed by a 0.36 N TMAH alkali developer, whereby the exposedarea remained, while the unexposed area was dissolved in the developer.Negative patterns were thus formed

TABLE II-6 Sensitivity Resolution Example Polymer (mJ/cm²) (μmL/S) Ex.II-33 Compound II-12 30 0.16 Ex. II-34 Compound II-13 33 0.16 Ex. II-35Compound II-14 35 0.18 Ex. II-36 Compound II-15 57 0.18 Ex. II-37Compound II-16 25 0.18 Ex. II-38 Compound II-17 60 0.17

[0234] From the data shown in the above table, it can be known that anegative pattern free from swelling can successfully be formed by theuse of any of these resists. Etching was conducted by using CF₄ plasma.It was found that the etching rates of these resists were 1.2 to 1.0time that of polyhydroxystyrene resin.

Examples II-9 to II-11 and Comparative Examples II-1 to II-5

[0235] The following homopolymers, Polymers 1 to 8, were obtained byradically polymerizing Monomers 1 to 8. The molecular weights of thesepolymers were approximately 10,000.

[0236] The glass transition temperatures (Tg) of these polymers weremeasured by a differential scanning calorimeter (DSC). The results areshown in Table II-7. TABLE II-7 Tg Found Tg Calcd. Polymer Ex. No. (°C.) (° C.) Polymer 1 Ex. II-9 160 156 Polymer 2 Comp. Ex. II-1 146 147Polymer 3 Comp. Ex. II-2 N.D. 146 Polymer 4 Comp. Ex. II-3 133 136Polymer 5 Ex. II-10 159 156 Polymer 6 Comp. Ex. II-4 135 138 Polymer 7Ex. II-11 154 152 Poymer 8 Comp. Ex. II-5 130 129

[0237] As is clear from the date shown in Table II-7, Polymer 1 (ExampleII-9) in which hydroxyl group or an esterified group thereof is combinedwith carbons at the two 3-position has a Tg about 10° C. higher thanthat of Polymer 2 (Comparative Example II-41) or Polymer 3 (ComparativeExample II-2) in which such a group is combined with only one tertiarycarbon atom, and a Tg 20° C. higher than that of Polymer 4 (ComparativeExample II-3) in which such a group is not combined with tertiary carbonatom at all.

[0238] Further, it can also be known that Polymer 5 (Example II-10) andPolymer 7 (Example II-11) having different types of aliphatic rings,hydroxyl group or an esterified group thereof being combined withcarbons at the two 3-position, have higher glass transitiontemperatures.

[0239] Furthermore, the glass transition temperatures of these polymersobtained by calculation are also shown in Table II-7. The calculationwas conducted by the Bicerano method on the CAche system. The valuesobtained by this calculation are almost the same as those obtained bythe experiment. In the step of post-exposure bake that is an essentialstep in the processing of a chemically amplified resist, it is necessaryto bake the resist at a temperature of 100 to 150° C. At this time, whenthe Tg of the resist is low, a pattern cannot successfully be formed.Therefore, the resist compositions of the present invention, prepared byusing the polymers according to the present invention whose glasstransition temperatures are high can provide resist patterns with highresolution.

Test Example II-1

[0240] Monomer 1 and tetrahydropyranyl were polymerized to obtain acopolymer. This copolymer is quite the same as Resist II-4 that was usedin Example II-1. By using this copolymer, a resist was prepared in thesame manner as in Example II-1. Further, a copolymer of Monomer 2 andtetrahydropyranyl was obtained in the same manner as in Example II-1,and a comparative resist was prepared by using this copolymer. By theuse of these resists, exposure and processing were conducted in the samemanner as in Example II-1 to obtain resist patterns.

[0241] As a result, it was found the following: when the resist preparedby using the copolymer with Monomer 1 was used, a pattern with an L/S of0.15 micrometers was obtained; while, when the resist prepared by usingthe copolymer with Monomer 2 was used, a pattern could not successfullybe obtained, and the L/S was only about 0.3 micrometers. The reason forthis is as follows: since the copolymer with Monomer 2 has a Tg lowerthan that of the copolymer with Monomer 1, the former copolymer becomesrubbery during the step of post-exposure bake, and the pattern wasfluidized.

Test Example II-2

[0242] 50 mol % of monomer 5 and 50 mol % of tetrahydropyranyl werepolymerized to obtain a copolymer. The polymerization method was thesame as that in Example II-1. By using this copolymer, a resist wasprepared in the same manner as in Example II-1. Further, in the samemanner as in Example II-1, 50 mol % of Monomer 6 and 50 mol % oftetrahydropyranyl were polymerized to obtain a copolymer, and acomparative resist was prepared by using this copolymer. By the use ofthese resists, exposure and processing were conducted in the same manneras in Example II-1 to obtain resist patterns.

[0243] As a result, it was found the following: when the resist preparedby using the copolymer with Monomer 5 was used, a pattern with an L/S of0.16 micrometers was obtained at 5.2 mJ/cm²; while, when the resistprepared by using the copolymer with Monomer 6 was used, a pattern couldnot successfully be formed, and the L/S was only about 0.4 micrometers.

[0244] The reason for this is as follows: since the copolymer withMonomer 5 has a Tg lower than that of the copolymer with Monomer 6, theformer copolymer becomes rubbery during the step of post-exposure bake,and the pattern was fluidized.

Test Example II-3

[0245] 50 mol % of Monomer 7 and 50 mol % of tetrahydropyranyl werepolymerized to obtain a copolymer. The polymerization method was thesame as that in Example II-1. By using this copolymer, a resist wasprepared in the same manner as in Example II-1. Further, in the samemanner as in Example II-1, 50 mol % of Monomer 8 and 50 mol % oftetrahydropyranyl were polymerized to obtain a copolymer, and acomparative resist was prepared by using this copolymer. By the use ofthese resists, exposure and processing were conducted in the same manneras in Example II-1 to obtain resist patterns.

[0246] As a result, it was found the following: when the resist preparedby using the copolymer with Monomer 7 was used, a pattern with an L/S of0.16 micrometers was formed at 5.2 mJ/cm²; while, when the resistprepared by using the copolymer with Monomer 6 was used, a pattern couldnot successfully be formed, and the L/S was only 0.4 micrometers.

[0247] The reason for this is as follows: since the copolymer withMonomer 8 has a Tg lower than that of the copolymer with Monomer 7, theformer copolymer becomes rubbery during the step of post-exposure bake,and the pattern was fluidized.

Examples II-12 to II-16 and Comparative Example II-6

[0248] [Synthesis of Starting Compounds]

[0249] One mol of 1,3-dihydroxyadamantane was stirred in an aceticacid-acetic anhydride solution of CrO₃, oxidizing agent, with heating.After carrying out the reaction for 8 hours, the reaction solution wasneutralized to obtain a mixture of polyhydroxylated compounds ofhydroxyadamantane. This mixture was partitioned by high performanceliquid chromatography to obtain 1,3,5-trihydroxyadamantane.

[0250] This 1,3,5-trihydroxyadamantane was dissolved in methylenechloride. To this solution were added a small amount of trimethylamine,and then an equimolar amount of trimethylsilyl chloride. Reaction wascarried out at room temperature. The reaction product was partitioned byhigh performance liquid chromatography to obtain1,3-dihydroxy-5-trimethylsiloxyadamantane.

[0251] The 1,3-dicarboxyadamantane was oxidized and partitionedsimilarly to obtain 1,3-dicarboxy-5-hydroxyadamantane.

[0252] The 1,3-dicarboxy-5-hydroxyadamantane was dissolved in THF, andreacted with an excessive amount of thionyl chloride under reflux for 4hours. The excessive thionyl chloride and solvent were distilled off toobtain 1,3-dichloroformyl-5-hydroxyadamantane, which was an acidchloride compound of the 1,3-dicarboxy-5-hydroxyadamantane.

[0253] The 1,3-dichloroformyl-5-hydroxyadamantane was dissolved inmethylene chloride. To this solution were added a small amount oftrimethylamine, and then an equimolar amount of trimethylsilyl chloride.Reaction was carried out at room temperature to obtain1,3-dichloroformyl-5-trimethylsiloxyadamantane.

[0254] [Synthesis of Resist Resins]

[0255] 0.05 mol of the 1,3-dihydroxy-5-trimethylsiloxyadamantane wasdissolved in THF. To this solution were added 0.040 mol of the1,3-dichloroformyl-5-trimethylsiloxyadamantane, and then 0.010 mol of1,3-dicarboxyl-5-hydroxy-adamantane. The mixture was stirred whilekeeping its temperature at room temperature, and, to this, a solution of0.1 mol of triethylamine in THF was gradually added dropwise. Afterstirring two hours, the mixture was stirred at room temperature for afurther two hours. The reaction solution was filtered, and thengradually added dropwise to water for reprecipitation. The precipitatewas dissolved again in THF. By adding tetrabutylammonium fluoride (TBAF)to this solution, trimethylsilyl was eliminated. The reaction solutionwas gradually added dropwise to water for reprecipitation, therebyobtaining Ester oligomer 1 (containing a polyacid anhydride). Themolecular weight of the oligomer was found to be 4,000. The chemicalformula of Ester Oligomer 1 is as follows:

[0256] 0.05 mol of the 1,3-dichloroformyl-5-trimethylsiloxyadamantanewas dissolved in THF. To this solution were added 0.040 mol of menthanediol, and then 0.010 mol of the 1,3-dicarboxy-5-hydroxyadamantane. Themixture was stirred while keeping its temperature at room temperature,and, to this, a solution of 0.1 mol of triethylamine in THF wasgradually added dropwise. After stirring for two hours, the reactionsolution was stirred for a further two hours at room temperature. Thereaction solution was filtered, and then gradually added dropwise towater for reprecipitation. The precipitate was dissolved again in THF.By adding TBAF to this solution, trimethylsilyl was eliminated. Thereaction solution was gradually added dropwise to water forreprecipitation to obtain Ester Oligomer 2 (containing a polyacidanhydride). The molecular weight of this oligomer was found to be 3,500.Ester Oligomer 2 has the following chemical formula:

[0257] 0.05 mol of the 1,3-dichloroformyl-5-trimethylsiloxyadamantanewas dissolved in THF. To this solution was added 0.050 mol of menthanediol. The mixture was stirred while keeping its temperature at roomtemperature, and, to this, a solution of 0.1 mol of triethylamine in THFwas gradually added dropwise. After stirring for two hours, the reactionsolution was stirred for a further four hours at room temperature. Thereaction solution was filtered, and then gradually added dropwise towater for reprecipitation. The precipitate was dissolved again in THF.By adding TBAF to this solution, trimethylsilyl was eliminated. Thereaction solution was gradually added dropwise to water forreprecipitation to obtain Ester Oligomer 3. The molecular weight of thisoligomer was found to be 3,000. Ester Oligomer 3 has the followingchemical formula:

[0258] [Synthesis of Comparative Polymer]

[0259] [Synthesis of Comparative Ester Oligomer]

[0260] 0.05 mol of 1,3-diacetylchloride adamantane was dissolved in THF.To this solution was added 0.05 mol of menthane diol. The mixture wasstirred while keeping its temperature at room temperature, and, to this,a solution of 0.1 mol of triethylamine in THF was gradually addeddropwise. After stirring for two hours, the reaction solution wasstirred for a further two hours at room temperature. The reactionsolution was filtered, and then gradually added dropwise to water. Theprecipitate was reprecipitated from a water-acetone solvent to obtainComparative Ester oligomer A. This oligomer has the following chemicalformula:

[0261] [Synthesis of Dissolution-Preventive Agents]

[0262] 0.1 Molar equivalent of beta-naphthol novolak was dissolved inTHF. This solution was stirred together with a sufficient amount ofdi-t-butyl dicarbonate in the presence of 0.1 mol of sodium hydroxide atroom temperature for 6 hours. The reaction solution was then mixed withwater, and extracted from ethyl acetate to obtain t-butoxycarbonylatednaphthol novolak (tBocNN) with a molecular weight of 3,000. The rate ofintroduction of naphthodicarbonyl into tBocNN was 100 mol % of the totalhydroxyl group.

[0263] To tert-butyl malonate was added, in THF, an equimolar amount ofsodium hydroxide. To this mixture was added bromomethyladamantyl ketone,and the mixture was stirred for 3 hours. The salt produced was filteredoff, and the filtrate was concentrated to obtain di-tert-butyl2-((1-adamantyl)carbonylmethyl) malonate (ADTB).

[0264] 1-Naphthol was condensed with glyoxylic acid in the presence ofoxalic acid catalyst to obtain a novolak compound. This compound wasdissolved in dihydropyrane. To this solution was added a catalyticamount of hydrochloric acid to obtain a pyranylated novolak compound(NV4THP).

[0265] [Preparation of Resists and Formation of Resist Patterns]

[0266] The above-synthesized resist resins and dissolution-preventiveagents, and TPS-105 or NAI-105 manufactured by Midori Kagaku Co., Ltd.,Japan, photo acid generator, were dissolved in cyclohexanone inaccordance with the formulations shown in Table II-8, thereby obtainingvarnishes of the resists of Examples II-12 to II-16. On the other hand,a comparative varnish was prepared by using the resist of ComparativeExample II-6 and TPS-105, photo acid generator, as shown in Table II-8.TABLE II-8 Acid Additive Generator Oligomer (%) (%) (%) Ex. II-12 EsterOligomer 1 (99) — TPS-105 (1) Ex. II-13 Ester Oligomer 1 (79) ADTP (20)NAI-105 (1) Ex. II-14 Ester Oligomer 1 (79) NV4THP (20) NAI-105 (1) Ex.II-15 Ester Oligomer 2 (99) — NAI-105 (1) Ex. II-16 Ester Oligomer 2(99) — NAI-105 (1) Comp. Ex. II-6 Comparative Ester — NAI-105 (1)Oligomer A (99)

[0267] Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper having an NA of 0.55,using as the light source, an ArF excimer laser, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by a mixture of a 2.38% aqueous solutionof tetramethylammonium hydroxide (TMH) and isopropyl alcohol toselectively dissolve and remove the exposed area, thereby formingpositive resist patterns. The sensitivities of these resists, and thedegrees of resolution of the resist patterns are shown in Table II-9.TABLE II-9 Sensitivity Resolution (mJ/cm² ) (μmL/S) Remarks Ex. II-12 140.15 Pattern Configuration: good Ex. II-13 12 0.14 PatternConfiguration: good Ex. II-14 22 0.15 Pattern Configuration: good Ex.II-15 15 0.14 Pattern Configuration: good Ex. II-16 20 0.15 PatternConfiguration: good Comp. Ex. II-6 13 0.15 Pattern peeled greatly

[0268] The data shown in Table II-9 demonstrate the following: when theresists of Examples II-12 to II-16 are used, resist patterns excellentin resolution can be formed at high sensitivities, and these resists areexcellent in transparency against light with a wavelength of 193 nm andin alkali developability; while, when the resist of Comparative ExampleII-6 is used, a resist pattern excellent in resolution cannot be formed,and the resist pattern readily peels off.

[0269] These resists were also evaluated in terms of dry-etchingresistance by measuring their etching rates in CF₄ plasma etching. As aresult, the following were found: the etching rate of the resistcontaining polyhydroxystyrene resin as its base resin being taken as1.0, the etching rate of the resist of Comparative Example II-6 was 1.0,while those of the resists of Examples II-12 to II-16 were from 0.9 to1.2. The resists of Examples II-12 to II-16 were thus confirmed to havehigh dry-etching resistance.

Examples II-17 to II-19

[0270] In THF, the following monomers, Compound II-18 and CompoundII-19, were mixed with each other in a ratio of 2:8. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-17. The molecular weight of this resin was found to be 12,000.

[0271] In THF, the following monomers, Compound II-20, Compound II-21and Compound II-22, were mixed in a ratio of 7:2:1. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-18. This resin was found to have a molecular weight of 47,000 with awide molecular weight distribution. It is assumed that a part of thepolymer is cross-linked three-dimensionally.

[0272] In THF, the following monomers, Compound II-23 and CompoundII-24, were mixed with each other in a ratio of 6:4. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-19. The molecular weight of this resin was found to be 17,000.

[0273] One part by weight of TPS-105 manufactured by Midori Kagaku Co.,Ltd., Japan was added as a photo acid generator to each one of theabove-synthesized polymers of Examples of II-17 to II-19. These mixtureswere respectively dissolved in cyclohexanone, and the solutions werefiltered to obtain varnishes of the resists of Examples II-17 to II-19.

[0274] Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.54,using an ArF excimer laser as the light source, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by a 2.38% aqueous solution oftetramethylammonium hydroxide (TMH) to selectively dissolve and removethe exposed area, thereby forming positive resist patterns. Thesensitivities of these resists, and the degrees of resolution of theresist patterns are shown in Table II-10. TABLE II-10 SensitivityResolution Resist (mJ/cm²) (μml/S) Ex. 11-17 13 0.15 Ex. 11-18 12 0.14Ex. 11-19 12 0.14

[0275] The data shown in Table II-10 demonstrate the following: when theresists of Examples II-17 to II-19 are used, resist patterns excellentin resolution can be formed at high sensitivities, and these resists areexcellent both in transparency against light with a wavelength of 193 nmand alkali developability.

[0276] These resists were also evaluated in terms of dry-etchingresistance by measuring their etching rates in CF₄ plasma etching. As aresult, the following were found: the etching rate of the resistcontaining a novolak resin as its base being taken as 1.0, the etchingrate of the resist of Comparative Example II-6 was 1.2, while those ofthe resists of Examples II-17 to II-19 were from 0.9 to 1.0. The resistsof Examples II-17 to II-19 were thus confirmed to have high dry-etchingresistance.

Examples II-20 and II-21

[0277] The following monomer, Compound II-26, and Compound II-19 weremixed with each other in THF in a ratio of 4:6. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-20. The molecular weight of this resin was found to be 10,000.

[0278] Compound II-20, and the following monomer, Compound II-27, weremixed with each other in THF in a ratio of 6:4. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-21. The molecular weight of this resin was found to be 12,000.

Examples II-22 and II-23

[0279] The following monomer, Compound II-28, and Compound II-19 weremixed with each other in THF in a ratio of 4:6. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a polymer of ExampleII-22. The molecular weight of this polymer was found to be 6,000.

[0280] The following monomer, Compound II-29, and Compound II-20 weremixed with each other in THF in a ratio of 2:8. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a polymer of ExampleII-23. The molecular weight of this polymer was found to be 7,500.

[0281] One part by weight of TPS-105 manufactured by Midori Kagaku Co.,Ltd., Japan was added, as a photo acid generator, to each one of theabove-synthesized resist resins of Examples of II-20 to II-23. Thesemixtures were respectively dissolved in cyclohexanone, and the solutionswere filtered to obtain varnishes of the resists of Examples II-20 toII-23.

[0282] Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using an ArF excimer laser as the light source, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by an aqueous solution oftetramethylammonium hydroxide (TMH) to selectively dissolve and removethe exposed area, thereby forming positive resist patterns. Thesensitivities of these resist resins and the degrees of resolution ofthe resist patterns are shown in Table II-11. TABLE II-11 SensitivityResolution Resist (mJ/cm² ) (μmL/S) Ex. II-20 10 0.14 Ex. II-21 11 0.14Ex. II-22 15 0.14 Ex. II-23 13 0.14

[0283] The resists of Examples II-20 to II-23 were also evaluated interms of dry-etching resistance by measuring their etching rates in CF₄plasma etching. As a result, it was confirmed that their dry-etchingresistance was 0.8 to 1.0 time that of novolak resin.

Examples II-24 and II-25 and Comparative Example II-7

[0284] The following monomers, Compound II-30 and Compound II-31, weremixed with each other in THF in a ratio of 4:6. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-24. The molecular weight of this resin was found to be 6,000.

[0285] The following monomers, Compound II-32 and Compound II-33, andmaleic anhydride were mixed in THF in a ratio of 3.5:3:3.5. To thismixture was added 10 mol % of AIBN, and copolymerization was conductedat 60° C. for 40 hours. The reaction solution was added dropwise tohexane. The precipitate was filtered off, and dried to obtain a resin ofExample II-21. The molecular weight of this resin was found to be 5,500.

[0286] As Comparative Example II-7, Compound II-32,2-acryloyloxy-7-hydroxy-methyltricyclodecane and maleic anhydride weremixed in THF in a ratio of 3.5:3:3.5. To this mixture was added 10 mol %of AIBN, and copolymerization was conducted at 60° C. for 40 hours. Thereaction solution was added dropwise to hexane. The precipitate wasfiltered off, and dried to obtain a resin of Comparative Example II-7.The molecular weight of this resin was found to be 9,000.

[0287] One part by weight of TPS-105 manufactured by Midori Kagaku Co.,Ltd., Japan was added, as a photo acid generator, to each one of theabove-synthesized resist resins of Examples of II-24 and II-25, andComparative Example II-7. These mixtures were respectively dissolved incyclohexanone, and the solutions were filtered to obtain varnishes ofthe resists of Examples II-24 and II-25 and of Comparative Example II-7.

[0288] Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using an ArF excimer laser as the light source, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by an aqueous solution oftetramethylammonium hydroxide (TMH) to selectively dissolve and removethe exposed area, thereby forming a positive resist pattern. Thesensitivities of the resist resins and the degrees of resolution of theresist patterns are shown in Table II-12. TABLE II-12 SensitivityResolution (mJ/cm²⁾ (μmL/S) Remarks Ex. II-24 12 0.14 PatternConfigulation: good Ex. II-25 17 0.13 Pattern Configulation: good Comp.Ex. II-7 55 0.5 Scummy

[0289] The data shown in Table II-12 demonstrate that remarkably goodeffects are obtained when the resin structure of the present inventionis combined with maleic anhydride. The resists of Examples II-24 andII-25 were also evaluated in terms of dry-etching resistance bymeasuring their etching rates inCF₄ plasma etching. As a result, it wasconfirmed that their dry-etching resistance was 0.8 to 1.0 time that ofnovolak resin. Examples III-1 to III-9 and Comparative Examples III-1 toIII-4

[0290] <Synthesis of Starting Compounds (Adamantane Compounds (Monomers)Having >C═O)>

[0291] [Synthesis of Compound (III-A) and Compound (III-B)]

[0292] One mol of 2-adamantyl ketone was stirred in an aceticacid-acetic anhydride solution of CrO₃, oxidizing agent, with heating.After carrying out the reaction for 8 hours, the reaction solution wasneutralized to obtain a mixture of polydroxylated compounds of adamantylketone. This mixture was partitioned by high performance liquidchromatography to obtain 1-hydroxy-4-adamantanone (Compound (III-A)),and 1,3-dihydroxy-6-adamantanone (Compound (III-B)).

[0293] [Synthesis of Compound (III-C)

[0294] In the same manner as in the synthesis of Compound (III-A) and(III-B), 1,3-dicarboxyadamantane was oxidized, and partition wasconducted to obtain 1,3-dicarboxy-6-adamantanone (Compound (III-C)).

[0295] [Synthesis of Compound (III-D)]

[0296] Compound (III-C) was dissolved in THF, and reacted with anexcessive amount of thionyl chloride for 4 hours under reflux. Theexcessive thionyl chloride and solvent were distilled off to obtain anacid chloride compound of Compound (III-C) (Compound (III-D)).

[0297] [Synthesis of Compound (III-E)]

[0298] Compound (III-A) was dissolved in THF, and stirred together withan equimolar amount of acrylic acid chloride. To this mixture was addeddropwise an excessive amount of triethylamine at room temperature, andthe mixture was stirred for 3 hours. The salt precipitated was filteredoff, and the filtrate was concentrated to obtain an acrylic ester ofCompound (III-A) (Compound (III-E)).

[0299] The ¹HNMR chart of this compound is shown in FIG. 4.

[0300] [Synthesis of Compound (III-F)]

[0301] Compound (III-E) and an equimolar amount of2,2′-dimethyl-1,3-dioxane-4,6-dione were stirred in pyridine at roomtemperature for one week. The reaction product was added dropwise towater to obtain 1-acryloyloxylated4-(5-adamatylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (Compound(III-F)). The ¹HNMR chart of this compound is shown in FIG. 5.

[0302] [Synthesis of Compound (III-G)]

[0303] Dihydropyrane was added to methacrylic acid by the use of an acidcatalyst to obtain tetrahydropyranyl methacrylate (Compound (III-G)).

[0304] [Synthesis of Compound (III-H)]

[0305] 1-Adamantanol and acrylic acid chloride were subjected todesalting reaction by the use of a basic catalyst to obtain adamantylacrylate (Compound (III-H)).

[0306] It is noted that methacrylic acid, menthane diol and1,3-dicarboxyl adamantane were reagents manufactured by Aldrich ChemicalCompany, Inc., and used as they were.

[0307] [Synthesis of Compound (III-I)]

[0308] 2-Methyl-2-adamantanol was dissolved in methylene chloride, andthe solution was stirred together with an equimolar amount of acrylicacid chloride. To this mixture was added dropwise an excessive amount oftriethylamine at room temperature, and the mixture was stirred for 3hours. The salt precipitated was filtered off, and the filtrate wasconcentrated to obtain an acrylic ester of 2-methyl-2-adamantanol(Compound (III-I)).

[0309] [Synthesis of Compound (III-J)]

[0310] Hydroxypinanone was dissolved in THF, and the solution wasstirred together with an equimolar amount of acrylic acid chloride. Tothis mixture was added dropwise an excessive amount of triethylamine atroom temperature, and the mixture was stirred for 3 hours. The saltprecipitated was filtered off, and the filtrate was concentrated toobtain an acrylic ester of hydroxypinanone (Comparative Monomer J).

[0311] <Synthesis of Resins>

[0312] 0.6 mol of Compound (III-E) and 0.4 mol of Compound (III-G) weremixed with 200 g of THF. Subsequently, 2 g of AIBN was added to thismixture, and the resulting mixture was heated at 60° C. for 36 hours.The reaction solution was added dropwise to hexane to obtain CopolymerIII-1 having an average molecular weight of approximately 7,000. Thestructural formula of Copolymer III-1 is as follows:

[0313] 0.6 mol of Compound (III-F) and 0.4 mol of Compound (III-G) weremixed with 200 g of THF. Subsequently, 2 g of AIBN was added to thismixture, and the resulting mixture was heated at 60° C. for 36 hours.The reaction solution was added dropwise to hexane to obtain CopolymerIII-2 having an average molecular weight of approximately 8,000. Thestructural formula of Copolymer III-2 is as follows:

[0314] 0.6 mol of Compound (III-E) and 0.4 mol of Compound (III-I) weremixed with 200 g of THF. Subsequently, 2 g of AIBN was added to thismixture, and the resulting mixture was heated at 60° C. for 36 hours.The reaction solution was added dropwise to hexane to obtain CopolymerIII-3 having an average molecular weight of approximately 5,000. Thestructural formula of Copolymer III-3 is as follows:

[0315] 0.04 mol of Compound (III-B) was dissolved in THF. To thissolution were added 0.05 mol of Compound (III-D), and then 0.010 mol ofCompound (III-C). The mixture was stirred while keeping its temperatureat room temperature, and, to this, a solution of 0.1 mol oftriethylamine in THF was gradually added dropwise. After stirring for 2hours, the mixture was stirred at room temperature for a further 2hours, and the reaction solution was filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated to obtain Ester Oligomer III-4 (containing a polyacidanhydride). The average molecular weight of this oligomer was found tobe 4,000. The structural formula of Ester oligomer III-4 is as follows:

[0316] 0.05 mol of Compound (III-D) was dissolved in THF. To thissolution were added 0.040 mol of menthane diol, and then 0.010 mol ofCompound (III-C). The mixture was stirred while keeping its temperatureat room temperature, and, to this, a solution of 0.1 mol oftriethylamine in THF was gradually added dropwise. After stirring for 2hours, the mixture was stirred at room temperature for a further 2hours, and the reaction solution was filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated to obtain Ester Oligomer III-5 (containing a polyacidanhydride). The average molecular weight of this oligomer was found tobe 3,500. The structural formula of Ester Oligomer III-5 is as follows:

[0317] 0.05 mol of Compound (III-D) was dissolved in THF. To thissolution was added 0.050 mol of menthane diol. The mixture was stirredwhile keeping its temperature at room temperature, and, to this, asolution of 0.1 mol of triethylamine in THF was gradually addeddropwise. After stirring for 2 hours, the mixture was stirred at roomtemperature for a further 4 hours, and the reaction solution wasfiltered. The filtrate was gradually added dropwise to water, and theprecipitate was reprecipitated to obtain Ester Oligomer III-6. Theaverage molecular weight of this oligomer was found to be 3,000. Thestructural formula of Ester Oligomer III-6 is as follows:

[0318] <Synthesis of Comparative Acrylate Polymers>

[0319] 0.6 mol of the adamatyl acrylate (Compound (III-H)) and 0.4 molof the tetrahydropyrany methacrylate (Compound (III-G)) were reactedwith each other in THF for 40 hours by the use of AIBN (10 mol %) as aninitiator. The reaction solution was added dropwise to hexane to obtainComparative Acrylate Polymer III-A. The structural formula of thispolymer is as follows:

[0320] 0.6 mol of Compound (III-J) and 0.4 mol of Compound (III-G) weremixed with 200 g of THF. Subsequently, 2 g of AIBN was added to thismixture, and the resulting mixture was heated at 60° C. for 36 hours.The reaction solution was added dropwise to hexane to obtain ComparativeAcrylate Polymer III-B having an average molecular weight ofapproximately 10,000. The structural formula of this polymer is asfollows:

[0321] 0.5 mol of Compound (III-E), 0.4 mol of Compound (III-G) and 0.1mol of methacrylic acid were mixed with 200 g of THF. Subsequently, 2 gof AIBN was added to this mixture, and the resulting mixture was heatedat 60° C. for 36 hours. The reaction solution was added dropwise tohexane to obtain Comparative Acrylate Polymer III-C having an averagemolecular weight of approximately 8,000. The structural formula of thispolymer is as follows:

[0322] <Synthesis of Comparative Ester Polymer>

[0323] 0.05 mol of adamantandicarbonyl chloride was dissolved in THF,and to this solution was added 0.05 mol of menthane diol. The mixturewas stirred while keeping its temperature at room temperature, and, tothis, a solution of 0.1 mol of trimethylamine in THF was gradually addeddropwise. After stirring for two hours, the reaction solution wasstirred for a further 2 hours, and then filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated from a water-acetone solvent to obtain Comparative EsterOligomer III-D. The structural formula of this oligomer is as follows:

[0324] <Synthesis of Dissolution-Preventive Agents>

[0325] Beta-naphthol novolak in an amount of 0.1 mol in terms ofnaphthol was dissolved in THF. This solution was stirred together with asufficient amount of di-t-butyl dicarbonate in the presence of 0.1 molof sodium hydroxide at room temperature for 6 hours. The reactionsolution was mixed with water, and extracted from ethyl acetate toobtain t-butoxycarbonylated naphthol novolak (tBocNN) having a molecularweight of 3,000. The rate of introduction of t-butoxycarbonyl into thetBocNN was 100 mol % of the total hydroxyl group.

[0326] To tert-butyl malonate was added, in THF, an equimolar amount ofsodium hydroxide. To this mixture was added bromomethyl amadantylketone, and the mixture was stirred for 3 hours. The salt precipitatedwas filtered off, and the filtrate was concentrated to obtaindi-tert-butyl 2-((1-amadantyl)carbonyl-methyl)malonate (ADTB).

[0327] 1-Naphthol was condensed with glyoxylic acid in the presence ofoxalic acid catalyst to obtain a novolak compound. This compound wasdissolved in dihydropyrane. To this solution was added a catalyticamount of hydrochloric acid to obtain a pyranylated novolak compound(NV4THP).

[0328] <Preparation of Resists & Formation of Resist Patterns>

[0329] The above-synthesized polymer compounds anddissolution-preventive agents, and TPS-105 or NAI-105 manufactured byMidori Kagaku Co., Ltd., Japan, photo acid generator, were dissolved incyclohexanone (polyester type) or PGMEA (acrylic type) in accordancewith the formulations shown in Tables III-1 and III-2 to obtainvarnishes of the resists of Examples III-1 to III-9. TABLE III-1 AcidPolymer or Oligomer Generator (%) Additive (%) (%) Ex. III-1 Copolymer 1(99) — TPS-105 (1) Ex. III-2 Copolymer 1 (79) t-BocNN (20) TPS-105 (1)Ex. III-3 Copolymer 2 (99) — TPS-105 (1) Ex. III-4 Copolymer 3 (99) —TPS-105 (1) Ex. III-5 Ester Oligomer 4 (99) — TPS-105 (1) Ex. III-6Ester Oligomer 4 (79) ADTB (20) NAI-105 (1) Ex. III-7 Ester Oligomer 4(79) NV4THP (20) NAI-105 (1) Ex. III-8 Ester Oligomer 5 (99) — NAI-105(1) Ex. III-9 Ester Oligomer 6 (99) — TPS-105 (1)

[0330] On the other hand, comparative varnishes III-1 to III-4 wereprepared by using the comparative polymers, and TPS-105, photo acidgenerator, as shown in Table III-2. TABLE III-2 Acid Polymer or OligomerGenerator (%) Additive (%) (%) Comp. Ex. III-1 Comparative Acryl —TPS-105 (1) Polymer A (99) Comp. Ex. III-2 Comparative Acryl — TPS-105(1) Polymer B (99) Comp. Ex. III-3 Comparative Acryl — TPS-105 (1)Polymer C (99) Comp. Ex. III-4 Comparative Acryl — TPS-105 (1) Polymer D(99)

[0331] Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicon wafers to form resist films, each having athickness of 0.3 micrometers. These resists films were respectivelyexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using as the light source an ArF excimer laser, thereby conductingpattern-wise exposure. Thereafter, these resist films were baked at 110°C. for 2 minutes, and then developed by a mixture of a 2.38% aqueoussolution of tetramethylammonium hydroxide (TMAH), MAH and isopropylalcohol. The exposed area was thus selectively dissolved and removed toform positive resist patterns. The sensitivities of the resist resins,and the degrees of resolution of the resist patterns are shown in TableIII-3. TABLE III-3 Sensitivity Resolution (mJ/cm²) (μmL/S) Remarks Ex.III-1 5 0.15 Good Ex. III-2 15 0.15 Good Ex. III-3 10 0.15 Good Ex.III-4 7 0.14 Good Ex. III-5 14 0.15 Good Ex. III-6 12 0.14 Good Ex.III-7 22 0.15 Good Ex. III-8 15 0.14 Good Ex. III-9 20 0.15 Good Comp.Ex. III-1 22 0.35 Impossible to form fine pattern Comp. Ex. III-2 100.19 Pattern peeled greatly Comp. Ex. III-3 7 0.17 Pattern peeledgreatly, used thin developer Comp. Ex. III-4 3 0.15 Pattern peeledgreatly

[0332] The date shown in Table III-3 demonstrate the following: when theresists of Examples III-1 to III-9 are used, resist patterns excellentin resolution can be formed at high sensitivities, and these resists areexcellent in both transparency against light with a wavelength of 193 nmand alkali developability; while, when the resists of Comparative III-1to III-3 are used, resist patterns excellent in resolution cannot beformed, and the resist films readily peel off.

[0333] In addition, these resists were evaluated in terms of dry-etchingresistance by measuring their etching rates in CF₄ plasma etching. As aresult, it was found the following: the etching rate of the resistcontaining as its base resin polyhydroxystyrene resin being taken as1.0, the etching rates of the resists of Comparative Examples III-1 andIII-4 are from 1.0 to 1.3 (moderate), and those of the resists ofComparative Examples III-2 and III-3 are approximately 1.4 to 1.6(poor); while the etching rates of the resists of Examples III-1 toIII-9 are from 0.9 to 1.2. The resists of Examples III-1 to III-9 arethus confirmed to have high dry-etching resistance.

Examples III-10 to III-18 and Comparative Examples III-5 to III-9

[0334] <Synthesis of Starting Compounds (Adamantane Compounds (Monomers)Having Lactonyl Group)>

[0335] [Synthesis of Compound (III-a) and Compound (III-b)]

[0336] One mol of 2-adamantyl ketone was stirred in an aceticacid-acetic anhydride solution of CrO₃, oxidizing agent, with heating.After carrying out the reaction for 8 hours, the reaction solution wasneutralized to obtain a mixture of polyhydroxylated compounds ofadamantyl ketone. This mixture was partitioned by high performanceliquid chromatography to obtain 1-hydroxy-4-adamantanone (Compound(III-a)) and 1,3-dihydroxy-6-adamantanone (Compound (III-b)).

[0337] [Synthesis of Compound (III-c)]

[0338] Similarly, 1,3-dicarboxyadamantane was oxidized, and partitionwas conducted to obtain 1,3-dicarboxy-6-adamantanone, Compound (III-c).

[0339] [Synthesis of Compound (III-d)]

[0340] Compound (III-c) was dissolved in THF, and reacted with anexcessive amount of thionyl chloride under ref lux for 4 hours. Theexcessive thionyl chloride and solvent were distilled off to obtain anacid chloride compound of Compound (III-c) (Compound (III-d)).

[0341] [Synthesis of Compound (III-a′)]

[0342] Compound (III-a) was dissolved in dichloromethane. To thissolution was added methachloroperbenzoic acid, and the mixture wasstirred at room temperature for 1 hour. The reaction solution was thentreated with diazomethane to obtain a lactone (Compound (III-a′)).

[0343] [Synthesis of Compound (III-b′)]

[0344] Compound (III-b) was dissolved in dichloromethane. To thissolution was added methachloroperbenzoic acid, and the mixture wasstirred at room temperature for 1 hour. The reaction solution was thentreated with diazomethane to obtain a lactone (Compound (III-b′)).

[0345] [Synthesis of Compound (III-c′)]

[0346] Similarly, 1,3-dicarboxyadamantane was oxidized, and partitionwas conducted to obtain a lactone (Compound (III-c′)).

[0347] [Synthesis of Compound (III-d′)]

[0348] Compound (III-c′) was dissolved in THF, and reacted with anexcessive amount of thionyl chloride under reflux for 4 hours. Theexcessive thionyl chloride and solvent were distilled off to obtain anacid chloride compound of Compound (III-c′) (Compound (III-d′)).

[0349] [Synthesis of Compound (III-e)]

[0350] Compound (III-a′) was dissolved in THF, and stirred together withan equimolar amount of acrylic acid chloride. To this mixture was addeddropwise an excessive amount of triethylamine at room temperature, andthe mixture was stirred for 3 hours. The precipitated salt was filteredoff, and the filtrate was concentrated to obtain an acrylic ester ofCompound (III-a′) (Compound III-e, R in the general formula (3) beingacryloyl group).

[0351] (Synthesis of Compound (III-f)]

[0352] Compound (III-b′) was dissolved in THF, and stirred with anequimolar amount of acrylic acid chloride. To this mixture was addeddropwise an excessive amount of triethylamine at room temperature, andthe mixture was stirred for 3 hours. The precipitated salt was filteredoff, and the filtrate was concentrated to obtain an acrylic ester ofCompound (III-b′) (Compound III-f, R in the general formula (4) beingacryloyl group).

[0353] [Synthesis of Compound (III-g)]

[0354] Dihydropyrane was added to methacrylic acid by the use of an acidcatalyst to obtain tetrahydropyranyl methacrylate (Compound (III-g)).

[0355] [Synthesis of Compound (III-h)]

[0356] 1-Adamantanol and acrylic acid chloride were subjected todesalting reaction by using a basic catalyst to obtain adamantylacrylate (Compound (III-h)).

[0357] Methacrylic acid, menthane diol and 1,3-dicarboxyl adamantane arereagents manufactured by Aldrich Chemical Company, Inc., and were usedas they were.

[0358] [Synthesis of Compound (III-i)]

[0359] 2-Methyl-2-adamantanol was dissolved in methylene chloride, andstirred together with an equimolar amount of acrylic acid chloride. Tothis mixture was added dropwise an excessive amount of triethylamine atroom temperature, and the mixture was stirred for 3 hours. Theprecipitated salt was filtered off, and the filtrate was concentrated toobtain an acrylic ester of 2-methyl-2-adamantanol (Compound (III-i)).

[0360] [Synthesis of Compound (III-j)]

[0361] Hydroxypinanone was dissolved in THF, and stirred together withan equimolar amount of acrylic acid chloride. To this mixture was addeddropwise an excessive amount of triethylamine at room temperature, andthe mixture was stirred for 3 hours. The precipitated salt was filteredoff, and the filtrate was concentrated to obtain an acrylic ester ofhydroxypinanone (Comparative Compound (III-j)).

[0362] <Synthesis of Resins>

[0363] 0.6 mol of Compound (III-e) and 0.4 mol of Compound (III-g) weremixed with 200 g of THF. To this mixture was then added 2 g of AIBN, andthe mixture was heated at 60° C. for 36 hours. The reaction solution wasadded dropwise to hexane to obtain Copolymer III-7 having an averagemolecular weight of approximately 7,000. The structural formula of thiscopolymer is as follows:

[0364] 0.6 mol of Compound (III-f) and 0.4 mol of Compound (III-g) weremixed with 200 g of THF. To this mixture was then added 2 g of AIBN, andthe mixture was heated at 60° C. for 36 hours. The reaction solution wasadded dropwise to hexane to obtain Copolymer III-8 having an averagemolecular weight of approximately 8,000. The structural formula of thiscopolymer is as follows:

[0365] 0.6 mol of Compound (III-e) and 0.4 mol of Compound (III-i) weremixed with 200 g of THF. To this mixture was then added 2 g of AIBN, andthe mixture was heated at 60° C. for 36 hours. The reaction solution wasadded dropwise to hexane to obtain Copolymer III-9 having an averagemolecular weight of approximately 5,000. The structural formula of thiscopolymer is as follows:

[0366] 0.05 mol of Compound (III-b′) was dissolved in THF. To thissolution were added 0.040 mol of Compound (III-d), and then 0.010 mol ofCompound (III-c). The mixture was stirred while maintaining itstemperature at room temperature, and, to this, a solution of 0.1 mol oftriethylamine in THF was gradually added dropwise. After stirring for 2hours, the mixture was stirred for a further 2 hours at roomtemperature, and then filtered. The filtrate was gradually addeddropwise to water, and the precipitate was reprecipitated to obtainEster Oligomer III-10 (containing a polyacid anhydride). The averagemolecular weight of this oligomer was found to be 4,000. The structuralformula of this oligomer is as follows:

[0367] 0.05 mol of Compound (III-d′) was dissolved in THF. To thissolution were added 0.040 mol of menthane diol, and then 0.010 mol ofCompound (III-c). The mixture was stirred while maintaining itstemperature at room temperature, and, to this, a solution of 0.1 mol oftriethylamine in THF was gradually added dropwise. After stirring for 2hours, the mixture was stirred for a further 2 hours at roomtemperature, and then filtered. The filtrate was gradually addeddropwise to water, and the precipitate was reprecipitated to obtainEster Oligomer III-11 (containing a polyacid anhydride). The averagemolecular weight of this oligomer was found to be 3,500. The structuralformula of this oligomer is as follows:

[0368] 0.05 mol of Compound (III-d′) was dissolved in THF. To thissolution was added 0.050 mol of menthane diol. The mixture was stirredwhile maintaining its temperature at room temperature, and, to this, asolution of 0.1 mol of triethylamine in THF was gradually addeddropwise. After stirring for 2 hours, the mixture was stirred for afurther 4 hours at room temperature, and then filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated to obtain Ester oligomer III-12. The average molecularweight of this oligomer was found to be 3,000. The structural formula ofthis oligomer is as follows:

[0369] [Synthesis of Comparative Acrylate Polymer]

[0370] 0.6 mol of the adamantyl acrylate (Compound (III-h)) and 0.4 molof the tetrahydropyranyl methacrylate (Compound (III-g)) were reactedwith each other in THF for 40 hours by using AIBN (10 mol %) as aninitiator. The reaction solution was added dropwise to hexane to obtainComparative Acrylate Polymer III-E. The structural formula of thispolymer is as follows:

[0371] [Synthesis of Comparative Ester Oligomer]

[0372] 0.05 mol of adamatandicarbonyl chloride was dissolved in THF, andto this solution was added 0.05 mol of menthane diol. The mixture wasstirred while maintaining its temperature at room temperature, and, tothis, a solution of 0.1 mol of triethylamine in THF was gradually addeddropwise. After stirring for two hours, the reaction solution wasstirred for a further 2 hours, and then filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated from a water-acetone solvent to obtain Comparative EsterOligomer III-F. The structural formula of this oligomer is as follows:

[0373] [Comparative Acrylate Polymer]

[0374] Comparative Acrylate Polymers III-G, III-H and III-I described inJapanese Patent Laid-Open Publication No.3169/1998, having the followinggeneral formulas were prepared.

[0375] [Preparation of Resists and Formation of Resist Patterns]

[0376] The above-synthesized polymer compounds anddissolution-preventive agents, and TPS-105 or NAI-105 manufactured byMidori Kagaku Co., Ltd., Japan, photo acid generator, were dissolved incyclohexanone (polyester type) or PGMEA (acrylic ester type) inaccordance with the formulations shown in Table III-4 obtain varnishesof the resists of Examples III-10 to III-18. TABLE III-4 Acid Polymer orOligomer Generator (%) Additive (%) (%) Ex. III-10 Copolymer 7 (99) —TPS-105 (1) Ex. III-11 Copolymer 7 (79) t-BocNN (20) TPS-105 (1) Ex.III-12 Copolymer 8 (99) — TPS-105 (1) Ex. III-13 Copolymer 9 (99) —TPS-105 (1) Ex. III-14 Ester Oligomer10 (99) — TPS-105 (1) Ex. III-15Ester Oligomer10 (79) ADTB (20) NAI-105 (1) Ex. III-16 Ester Oligomer10(79) NV4THP (20) NAI-105 (1) Ex. III-17 Ester Oligomer11 (99) — NAI-105(1) Ex. III-18 Ester Oligomer12 (99) — TPS-105 (1)

[0377] On the other hand, varnishes of the resists of ComparativeExamples III-5 to III-9 were prepared by using the comparative polymers,and, as a photo acid generator, TPS-105 as shown in Table III-5. TABLEIII-5 Acid Polymer or Oligomer Generator (%) Additive (%) (%) Comp. Ex.III-5 Comparative Acryl — TPS-105 (1) Polymer E (99) Comp. Ex. III-6Comparative Acryl — TPS-105 (1) Polymer F (99) Comp. Ex. III-7Comparative Acryl — TPS-105 (1) Polymer G (99) Comp. Ex. III-8Comparative Acryl — TPS-105 (1) Polymer H (99) Comp. Ex. III-9Comparative Acryl — TPS-105 (1) Polymer I (99)

[0378] Subsequently, the varnishes of these resists were respectivelyspin-coated onto silicon wafers to form resist films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using as the light source an ArF excimer laser, thereby conductingpattern-wise exposure. The resist films were then baked at 110° C. for 2minutes, and developed by a mixture of a 2.38% aqueous solution oftetramethyl-ammonium hydroxide (TMAH), MAH and isopropyl alcohol. Theexposed area was thus selectively dissolved and removed to form positiveresist patterns. The sensitivities of the resists, and the degrees ofresolution of the resist patterns are as shown in Table III-6. TABLEIII-6 Sensitivity Resolution (mJ/cm²) (μmL/S) Remarks Ex. III-10 5 0.15Good Ex. III-11 15 0.15 Good Ex. III-12 10 0.15 Good Ex. III-13 7 0.14Good Ex. III-14 14 0.15 Good Ex. III-15 12 0.14 Good Ex. III-16 22 0.15Good Ex. III-17 15 0.14 Good Ex. III-18 20 0.15 Good Comp. Ex. III-5 220.35 Impossible to form fine pattern Comp. Ex. III-6 10 0.19 Patternpeeled greatly Comp. Ex. III-7 13 0.35 Impossible to form fine patternComp. Ex. III-8 20 0.35 Impossible to form fine pattern Comp. Ex. III-913 0.20 Pattern peeled greatly

[0379] The date shown in Table III-6 demonstrate the following: when theresists of Examples of III-10 to III-18 are used, resist patternsexcellent in resolution are formed at high sensitivities, and theresists are excellent in both transparency against light of 193 nm andalkali developability; while, when the resists of Comparative ExamplesIII-5 to III-9 are used, resist patterns excellent in resolution cannotbe formed, and the resist films readily peel off.

[0380] In addition, these resists were evaluated in terms of dry-etchingresistance by measuring their etching rates in CF₄ plasma etching. As aresult, the following were found: the etching rate of the resistcontaining as its base resin polyhydroxystyrene resin being taken as1.0, the etching rates of the resists of Comparative Examples III-5 andIII-6 were from 1.0 to 1.3 (moderate), and those of the resists ofComparative Examples III-7, III-8 and III-9 were approximately 1.4 to1.6 (poor); while the etching rates of the resists of Examples III-10 toIII-18 were from 0.9 to 1.2. The resists of Examples III-10 to III-18were thus confirmed to have high dry-etching resistance.

1. A process for producing a semiconductor device, comprising the stepsof: forming, on an etching film formed on a substrate, a film containinga resist composition which comprises a resist resin obtained byhomopolymerizing at least one monomer selected from monomers representedby the general formulas (I-1) and (I-2):

wherein r is acryloyl or methacryloyl group, R₁₁ and R₁₂ are hydrogenatom or a monovalent alkyl group, and R₁₃ is oh group, ═O group, COOHgroup or COOR₁₄ group (R₁₄ is a monovalent organic group), or bycopolymerizing the monomer(s) and any other vinyl monomer, and a photoacid generator, subjecting the film coated onto the substrate topattern-wise exposure, developing the film exposed to light, therebyforming a patterned photomask, and etching an etching film by dryetching, using the photomask as a mask.
 2. The process for producing asemiconductor device according to claim 1, wherein R₁₃ is ═O group. 3.The process for producing a semiconductor device according to claim 1,wherein at least one of R₁₁ and R₁₂ contained in the resist resin isselected from the group consisting of C₂H₅ group, C₃H₇ group and C₄H₉group.
 4. The process for producing a semiconductor device according toclaim 1, wherein R₁₃ is combined with a tertiary carbon atom.
 5. Aresist composition comprising: a resist resin obtained by copolymerizingat least one monomer selected from monomers represented by the generalformulas (I-1) and (I-2):

and at least one monomer selected from monomers represented by thegeneral formulas (I-3), (I-4), (I-5), (I-6) and (I-7):

wherein R₃₁ is hydrogen atom, or at least one group selected from thegroup consisting of OH group, OR₁₄ group (R₁₄ is a monovalent organicgroup) and ═O group, R₃₂ is hydrogen atom or a monovalent organic group,and R₄₁ is vinyl, acryloyl or methacryloyl group; and a photo acidgenerator.
 6. A pattern forming process comprising the steps of:forming, on a substrate, a film containing the resist composition setforth in claim 5, subjecting the film to pattern-wise exposure, anddeveloping the film exposed to light.
 7. A resist resin having abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring.
 8. A resist compositioncomprising: a resin having a bridged-bond-containing aliphatic ring, atleast two oxygen-containing polar groups being combined with a tertiarycarbon atom of the bridged-bond-containing aliphatic ring, and a photoacid generator.
 9. The resist composition according to claim 8, whereinthree or more oxygen-containing polar groups are combined with atertiary carbon atom of the bridged-bond-containing aliphatic ring. 10.The resist composition according to claim 8, wherein thebridged-bond-containing aliphatic ring is at least one ring selectedfrom the group consisting of adamantane ring, tricyclodecane ring,tetracyclododecane ring and norbornane ring.
 11. The resist compositionaccording to claim 8, wherein at least one of the oxygen-containingpolar groups is at least one organic group selected from the groupconsisting of substituted or unsubstituted carboxylic groups,substituted or unsubstituted hydroxyl groups, and substituentscontaining cyclic lactones.
 12. The resist composition according toclaim 8, wherein at least one of the oxygen-containing polar groups iscarboxyl group protected by a soluble group that can be decomposed by anacid.
 13. The resist composition according to claim 8, wherein the resincontains acid anhydride structure, and at least one of theoxygen-containing polar groups is hydroxyl group.
 14. A resistcomposition comprising: a resin comprising a polymer or condensate of amonomer having a bridged-bond-containing aliphatic ring, at least twooxygen-containing polar groups being combined with a tertiary carbonatom of the bridged-bond-containing aliphatic ring, and a photo acidgenerator.
 15. The resist composition according to claim 14, whereinthree or more oxygen-containing polar groups are combined with atertiary carbon atom of the bridged-bond-containing aliphatic ring. 16.The resist composition according to claim 14, wherein the resin is apolymer of a monomer having a bridged-bond-containing aliphatic ring, atleast two oxygen-containing polar groups being combined with a tertiarycarbon atom of the bridged-bond-containing aliphatic ring, and at leastone of the oxygen-containing polar groups combined with thebridged-bond-containing aliphatic ring in the monomer is acryloyloxy ormethacryloyloxy group.
 17. The resist composition according to claim 14,wherein the resin is a polymer of a monomer having abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring, and the monomer is a compoundrepresented by the following general formula (II-1):

wherein R₁ is acryloyl or methacryloyl group, R₂ is hydrogen atom or anoxygen-containing polar group, and R₃ is hydrogen atom, a groupdecomposable by an acid, a cyclic substituent having a lactone, or asubstituent having acid anhydride structure formed with abridged-bond-containing alicyclic compound containing a carboxylic acid.18. The resist composition according to claim 14, wherein the resin is apolymer of a monomer containing a bridged-bond-containing aliphaticring, at least two oxygen-containing polar groups being combined with atertiary carbon atom of the bridged-bond-containing aliphatic ring, andthe monomer is a compound represented by the following general formula(II-2):

wherein R₁ is acryloyl or methacryloyl group, R₂ is hydrogen atom or anoxygen-containing polar group, and R₄ is hydrogen atom, a cyclicsubstituent having a lactone, or a substituent containing acid anhydridestructure formed with a bridged-bond-containing alicyclic compoundhaving a carboxylic acid.
 19. The resist composition according to claim14, wherein the resin is an alicyclic-backbone-type resin obtainable bythe dehydration condensation of a monomer having abridged-bond-containing aliphatic ring, two or more organic groups of atleast one of carboxyl group and hydroxyl group being combined with atertiary carbon atom of the ring.
 20. A pattern forming processcomprising the steps of: forming, on a substrate, a film containing aresist composition which comprises a resin having abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring, and a photo acid generator,subjecting the film to pattern-wise exposure, and developing the filmexposed to light.
 21. A process for producing a semiconductor device,comprising the steps of: forming, on an etching film on a substrate, afilm containing a resist composition which comprises a resin having abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring, and a photo acid generator,subjecting the film coated onto the substrate to pattern-wise exposure,developing the film exposed to light, thereby forming a patternedphotomask, and etching an etching film by dry etching, using thephotomask as a mask.
 22. A resist composition comprising a resist resinhaving a bridged-bond-containing aliphatic ring composed of at least tworings selected from the group consisting of 5-membered rings, 6-memberedrings and 7-membered rings, and a photo acid generator, wherein at leastone carbon constituting the bridged-bond-containing aliphatic ringcontained in the resin is combined with oxygen through double bond. 23.The resist composition according to claim 22, wherein the resist resincomprises a unit obtained by polymerizing a monomer that is an acrylateor methacrylate compound having a bridged-bond-containing aliphatic ringcomposed of at least two rings selected from the group consisting of5-membered rings, 6-membered rings and 7-membered rings.
 24. The resistcomposition according to claim 22, wherein the resist resin comprises,as a polymer unit, at least one compound selected from compoundsrepresented by the following general formulas (III-1a), (III-1b),(III-2a) and (III-2b):

wherein R represents acryloyl or methacryloyl group, and R₁ and R₂represent an alkyl group or a group decomposable by an acid.
 25. Theresist composition according to claim 22, wherein at least one of therings constituting the bridged-bond-containing aliphatic ring containedin the resist resin is a lactone ring.
 26. The resist compositionaccording to claim 22, wherein the resist resin comprises, as a polymerunit, at least one compound selected from compounds represented by thefollowing general formulas (III-3a), (III-3b), (III-3c) and (III-4):

wherein R and R₁ represent acryloyl or methacryloyl group.
 27. Theresist composition according to claim 22, wherein the resist resin isselected from the group consisting of polyesters and polyacidanhydrides.
 28. The resist composition according to claim 22, whereinthe resist resin is obtained by copolymerization, using a comonomercapable of releasing its bridged-bond-containing aliphatic ring in thepresence of an acid to form a carboxylic acid.
 29. A pattern formingprocess comprising the steps of: forming, on a substrate, a filmcontaining a resist composition which comprises a resist resin having abridged-bond-containing aliphatic ring composed of at least two ringsselected from the group consisting of 5-membered rings, 6-membered ringsand 7-membered rings, and a photo acid generator, wherein at least onecarbon constituting the bridged-bond-containing aliphatic ring containedin the resin is combined with oxygen through double bond, subjecting thefilm to pattern-wise exposure, and developing the film exposed to light.